The Preamble states:

“ We the People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defence, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity, do ordain and establish this Constitution for the United States of America. ”

The Preamble does not grant any particular authority to the federal government and it does not prohibit any particular authority. What it does, is establish the fact that the federal government has no authority outside of what follows the preamble, as amended. "We the people", is one of the most-quoted sections of the Constitution. It was thought by federalists during this time that there was no need for a bill of rights and they thought that the preamble spelled out the people's rights.

Article One establishes the legislative branch of government, the United States Congress, which includes the House of Representatives and the Senate. The Article establishes the manner of election and qualifications of members of each House. For the House a representative must be 25 years old, have been a citizen of the United States for 7 years, and live in the state they represent. For the Senate a representative must be 30 years old, have been a citizen for 9 years, and live in the state they represent. In addition, it provides for free debate in Congress and limits self-serving behavior of congressmen, outlines legislative procedure and indicates the powers of the legislative branch. There is a debate as to whether the enumerated powers listed in Article 1 Section 8 are a list of enumerated powers. These powers may also be interpreted as a list of powers, formerly either executive or judicial in nature, that have been explicitly granted to the U.S. Congress. This interpretation may be further supported by a broad definition of both the commerce clause and the necessary-and-proper clause of the Constitution. The argument for enumerated powers can be traced back to the 1819 McCulloch v. Maryland United States Supreme Court ruling. Finally, it establishes limits on federal and state legislative power.

Article Two describes the presidency (the executive branch): procedures for the selection of the president, qualifications for office, the oath to be affirmed and the powers and duties of the office. It also provides for the office of Vice President of the United States, and specifies that the Vice President succeeds to the presidency if the President is incapacitated, dies, or resigns. The original text ("the same shall devolve") leaves it unclear whether this succession was intended to be on an acting basis (merely taking on the powers of the office) or permanent (assuming the Presidency itself). After the death of William Henry Harrison, John Tyler set the precedent that the succession was permanent, and this was followed in practice; the 25th Amendment explicitly states that the Vice President becomes President in those cases. Article Two also provides for the impeachment and removal from office of civil officers (the President, Vice President, judges, and others).

Article Three describes the court system (the judicial branch), including the supreme Court. The article requires that there be one court called the supreme Court; Congress, at its discretion, can create lower courts, whose judgments and orders are reviewable by the supreme Court. Article Three also requires trial by jury in all criminal cases, defines the crime of treason, and charges Congress with providing for a punishment for it. It also sets the kinds of cases that may be heard by the federal judiciary, which cases the supreme Court may hear first (called original jurisdiction), and that all other cases heard by the supreme Court are by appeal under such regulations as the Congress shall make.

Article Four describes the relationship between the states and the Federal government and amongst the states. For instance, it requires states to give "full faith and credit" to the public acts, records and court proceedings of the other states. Congress is permitted to regulate the manner in which proof of such acts, records or proceedings may be admitted. The "privileges and immunities" clause prohibits state governments from discriminating against citizens of other states in favor of resident citizens (e.g., having tougher penalties for residents of Ohio convicted of crimes within Michigan). It also establishes extradition between the states, as well as laying down a legal basis for freedom of movement and travel amongst the states. Today, this provision is sometimes taken for granted, especially by citizens who live near state borders; but in the days of the Articles of Confederation, crossing state lines was often a much more arduous (and costly) process. Article Four also provides for the creation and admission of new states. The Territorial Clause gives Congress the power to make rules for disposing of Federal property and governing non-state territories of the United States. Finally, the fourth section of Article Four requires the United States to guarantee to each state a republican form of government, and to protect the states from invasion and violence.

Article Five describes the process necessary to amend the Constitution. It establishes two methods of proposing amendments: by Congress or by a national convention requested by the states. Under the first method, Congress can propose an amendment by a two-thirds vote (of a quorum, not necessarily of the entire body) of the Senate and of the House of Representatives. Under the second method, two-thirds (2/3) of the state legislatures may convene and "apply" to Congress to hold a national convention, whereupon Congress must call such a convention for the purpose of considering amendments. As of 2008, only the first method (proposal by Congress) has been used.

Once proposed—whether submitted by Congress or by a national convention—amendments must then be ratified by three-fourths (3/4) of the states to take effect. Article Five gives Congress the option of requiring ratification by state legislatures or by special conventions assembled in the states. The convention method of ratification has been used only once (to approve the 21st Amendment). Article Five currently places only one limitation on the amending power—that no amendment can deprive a state of its equal representation in the Senate without that state's consent (limitations regarding slavery and taxation having expired in 1808).

Article Six establishes the Constitution, and the laws and treaties of the United States made in accordance with it, to be the supreme law of the land, and that "the judges in every state shall be bound thereby, any thing in the laws or constitutions of any state notwithstanding." It also validates national debt created under the Articles of Confederation and requires that all federal and state legislators, officers, and judges take oaths or affirmations to support the Constitution. This means that the states' constitutions and laws should not conflict with the laws of the federal constitution—and that in case of a conflict, state judges are legally bound to honor the federal laws and constitution over those of any state.

Article Six also states "no religious Test shall ever be required as a Qualification to any Office or public Trust under the United States".

Article Seven sets forth the requirements for ratification of the Constitution. The Constitution would not take effect until at least nine states had ratified the Constitution in state conventions specially convened for that purpose. (See above Drafting and ratification requirements.)

The authors of the Constitution were clearly aware that changes would be necessary from time to time if the Constitution was to endure and cope with the effects of the anticipated growth of the nation. However, they were also conscious that such change should not be easy, lest it permit ill-conceived and hastily passed amendments. Balancing this, they also wanted to ensure that an overly rigid requirement of unanimity would not block action desired by the vast majority of the population. Their solution was to devise a dual process by which the Constitution could be altered.

Unlike many other constitutions, amendments to the U.S. constitution are appended to the existing body of the text without altering or removing what already exists. There is no provision for deleting either obsolete text or rescinded provisions.

Aside from the direct process of amending the Constitution, court interpretation is also influenced by prior/existing judicial decisions. The United States is a common law country and its common law is rooted in English common law which means that courts acknowledge interpretations established in prior cases. These are referred to, collectively, as precedents. Nonetheless, local court decisions are subject to decisions written by the U.S. Supreme Court, whose responsibility it is to interpret the U.S. Constitution.) Not long after adoption of the Constitution, in the 1803 case of Marbury v. Madison the Supreme Court established the doctrine of judicial review, which is the power of the Court to examine legislation and other acts of Congress and to decide their constitutionality. The doctrine also embraces the power of the Court to explain the meaning of various sections of the Constitution as they apply to particular cases brought before the Court. Since such cases will reflect changing legal, political, economic, and social conditions, this provides a mechanism, in practice, for adjusting the Constitution without needing to amend its text. Over the years, a series of Court decisions, on issues ranging from governmental regulation of radio and television to the rights of the accused in criminal cases, has affected a change in the way many Constitutional clauses are interpreted, without amendment to the actual text of the Constitution.

Congressional legislation, passed to implement provisions of the Constitution or to adapt those implementations to changing conditions, also broadens and, in subtle ways, changes the meanings given to the words of the Constitution. Up to a point, the rules and regulations of the many agencies of the federal government have a similar effect. In case of objection, the test in both cases is whether, in the opinion of the courts, such legislation and rules conform with the meanings given to the words of the Constitution.

The Constitution has a total of 27 amendments. The first ten, collectively known as the Bill of Rights, were ratified simultaneously. The following seventeen were ratified separately.

The Bill of Rights comprises the first ten amendments to the Constitution. Those amendments were adopted between 1789 and 1791, and all relate to limiting the power of the federal government. They were added in response to criticisms of the Constitution by the state ratification conventions and by prominent individuals such as Thomas Jefferson (who was not a delegate to the Constitutional Convention). These critics argued that without further restraints, the strong central government would become tyrannical. The amendments were proposed by Congress as part of a block of twelve in September 1789. By December 1791 a sufficient number of states had ratified ten of the twelve proposals, and the Bill of Rights became part of the Constitution.

It is commonly understood that the Bill of Rights was not originally intended to apply to the states, though except where amendments refer specifically to the Federal Government or a branch thereof (as in the first amendment, under which some states in the early years of the nation officially established a religion), there is no such delineation in the text itself. Nevertheless, a general interpretation of inapplicability to the states remained until 1868, when the Fourteenth Amendment was passed, which stated, in part, that:

“ No State shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any State deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws. ”

The Supreme Court has interpreted this clause to extend most, but not all, parts of the Bill of Rights to the states. Nevertheless, the balance of state and federal power has remained a battle in the Supreme Court.

The amendments that became the Bill of Rights were actually the last ten of the twelve amendments proposed in 1789. The second of the twelve proposed amendments, regarding the compensation of members of Congress, remained unratified until 1992, when the legislatures of enough states finally approved it and, as a result, it became the Twenty-seventh Amendment despite more than two centuries of pendency. The first of the twelve—still technically pending before the state legislatures for ratification—pertains to the apportionment of the United States House of Representatives after each decennial census. The most recent state whose lawmakers are known to have ratified this proposal is Kentucky in 1792, during that commonwealth's first month of statehood.

First Amendment: addresses the rights of freedom of religion (prohibiting Congressional establishment of a religion over another religion through Law and protecting the right to free exercise of religion), freedom of speech, freedom of the press, freedom of assembly, and freedom of petition.

Second Amendment: declares "a well regulated militia" as "necessary to the security of a free State", and as explanation for prohibiting infringement of "the right of the People to keep and bear arms."

Third Amendment: prohibits the government from using private homes as quarters for soldiers without the consent of the owners. The only existing case law regarding this amendment is a lower court decision in the case of Engblom v. Carey.

Fourth Amendment: guards against searches, arrests, and seizures of property without a specific warrant or a "probable cause" to believe a crime has been committed. Some rights to privacy have been inferred from this amendment and others by the Supreme Court.

Fifth Amendment: forbids trial for a major crime except after indictment by a grand jury; prohibits double jeopardy (repeated trials), except in certain very limited circumstances; forbids punishment without due process of law; and provides that an accused person may not be compelled to testify against themself (this is also known as "Taking the Fifth" or "Pleading the Fifth"). This is regarded as the "rights of the accused" amendment. It also prohibits government from taking private property without "just compensation," the basis of eminent domain in the United States.

Sixth Amendment: guarantees a speedy public trial for criminal offenses. It requires trial by a jury, guarantees the right to legal counsel for the accused, and guarantees that the accused may require witnesses to attend the trial and testify in the presence of the accused. It also guarantees the accused a right to know the charges against him. The Sixth Amendment has several court cases associated with it, including Powell v. Alabama, United States v. Wong Kim Ark, Gideon v. Wainwright, and Crawford v. Washington. In 1966, the Supreme Court ruled that the fifth amendment prohibition on forced self-incrimination and the sixth amendment clause on right to counsel were to be made known to all persons placed under arrest, and these clauses have become known as the Miranda rights.

Seventh Amendment: assures trial by jury in civil cases.

Eighth Amendment: forbids excessive bail or fines, and cruel and unusual punishment.

Ninth Amendment: declares that the listing of individual rights in the Constitution and Bill of Rights is not meant to be comprehensive; and that the other rights not specifically mentioned are retained elsewhere by the people.

Tenth Amendment: provides that powers that the Constitution does not delegate to the United States and does not prohibit the states from exercising, are "reserved to the States respectively, or to the people."

Amendments to the Constitution subsequent to the Bill of Rights cover many subjects. The majority of the seventeen later amendments stem from continued efforts to expand individual civil or political liberties, while a few are concerned with modifying the basic governmental structure drafted in Philadelphia in 1787. Although the United States Constitution has been amended a total of 27 times, only 26 of the amendments are currently used because the 21st amendment supersedes the 18th.

Eleventh Amendment (1795): Clarifies judicial power over foreign nationals, and limits ability of citizens to sue states in federal courts and under federal law.

Twelfth Amendment (1804): Changes the method of presidential elections so that members of the electoral college cast separate ballots for president and vice president.

Thirteenth Amendment (1865): Abolishes slavery and grants Congress power to enforce abolition.

Fourteenth Amendment (1868): Defines a set of guarantees for United States citizenship; prohibits states from abridging citizens' privileges or immunities and rights to due process and the equal protection of the law; repeals the Three-fifths compromise; prohibits repudiation of the federal debt caused by the Civil War.

Fifteenth Amendment (1870): Forbids the federal government and the states from using a citizen's race, color, or previous status as a slave as a qualification for voting.

Sixteenth Amendment (1913): Authorizes unapportioned federal taxes on income.

Seventeenth Amendment (1913): Establishes direct election of senators.

Eighteenth Amendment (1919): Prohibited the manufacturing, importing, and exporting of alcoholic beverages (see Prohibition in the United States). Repealed by the Twenty-First Amendment.

Nineteenth Amendment (1920): Prohibits the federal government and the states from forbidding any citizen to vote due to their sex.

Twentieth Amendment (1933): Changes details of Congressional and presidential terms and of presidential succession.

Twenty-first Amendment (1933): Repeals Eighteenth Amendment. Permits states to prohibit the importation of alcoholic beverages.

Twenty-second Amendment (1951): Limits president to two terms.

Twenty-third Amendment (1961): Grants presidential electors to the District of Columbia.

Twenty-fourth Amendment (1964): Prohibits the federal government and the states from requiring the payment of a tax as a qualification for voting for federal officials.

Twenty-fifth Amendment (1967): Changes details of presidential succession, provides for temporary removal of president, and provides for replacement of the vice president.

Twenty-sixth Amendment (1971): Prohibits the federal government and the states from forbidding any citizen of age 18 or greater to vote simply because of their age.

Twenty-seventh Amendment (1992): Limits congressional pay raises.

Over 10,000 Constitutional amendments have been introduced in Congress since 1789; in a typical Congressional year in the last several decades, between 100 and 200 are offered. Most of these concepts never get out of Congressional committee, and far fewer get proposed by the Congress for ratification. Backers of some amendments have attempted the alternative, and thus-far never-utilized, method mentioned in Article Five. In two instances—reapportionment in the 1960s and a balanced federal budget during the 1970s and 1980s—these attempts have come within just two state legislative "applications" of triggering that alternative method.

Of the thirty-three amendments that have been proposed by Congress, six have failed ratification by the required three-quarters of the state legislatures—and four of those six are still technically pending before state lawmakers (see Coleman v. Miller). Starting with the 18th Amendment, each proposed amendment (except for the 19th Amendment and for the still-pending Child Labor Amendment of 1924) has specified a deadline for passage. The following are the unratified amendments:

The Congressional Apportionment Amendment, proposed by the 1st Congress on September 25, 1789, defined a formula for how many members there would be in the United States House of Representatives after each decennial census. Ratified by eleven states, the last being Kentucky in June 1792 (Kentucky's initial month of statehood), this amendment contains no expiration date for ratification. In principle it may yet be ratified, though as written it became moot when the population of the United States reached ten million.

The so-called missing thirteenth amendment, or "Titles of Nobility Amendment" (TONA), proposed by the 11th Congress on May 1, 1810, would have ended the citizenship of any American accepting "any Title of Nobility or Honour" from any foreign power. Some maintain that the amendment was actually ratified by the legislatures of enough states, and that a conspiracy has suppressed it, but this has been thoroughly debunked [1]. Known to have been ratified by lawmakers in twelve states, the last in 1812, this amendment contains no expiration date for ratification. It may yet be ratified.

The Corwin amendment, proposed by the 36th Congress on March 2, 1861, would have forbidden any attempt to subsequently amend the Constitution to empower the Federal government to "abolish or interfere" with the "domestic institutions" of the states (a delicate way of referring to slavery). It was ratified by only Ohio and Maryland lawmakers before the outbreak of the Civil War. Illinois lawmakers—sitting as a state constitutional convention at the time—likewise approved it, but that action is of questionable validity. The proposed amendment contains no expiration date for ratification and may yet be ratified. However, adoption of the 13th, 14th, and 15th Amendments after the Civil War likely means that the amendment would be ineffective if adopted.

A child labor amendment proposed by the 68th Congress on June 2, 1924, which stipulates: "The Congress shall have power to limit, regulate, and prohibit the labor of persons under eighteen years of age." This amendment is now moot, since subsequent federal child labor laws have uniformly been upheld as a valid exercise of Congress' powers under the commerce clause. This amendment contains no expiration date for ratification. It may yet be ratified.

Properly placed in a separate category from the other four constitutional amendments that Congress proposed to the states, but which not enough states have approved, are the following two offerings which—because of deadlines—are no longer subject to ratification.

The Equal Rights Amendment, or ERA, which reads in pertinent part "Equality of rights under the law shall not be denied or abridged by the United States or by any state on account of sex." Proposed by the 92nd Congress on March 22, 1972, it was ratified by the legislatures of 35 states, and expired on either March 22, 1979 or on June 30, 1982, depending upon one's point of view of a controversial three-year extension of the ratification deadline, which was passed by the 95th Congress in 1978. Of the 35 states ratifying it, four later rescinded their ratifications prior to the extended ratification period which commenced March 23, 1979 and a fifth—while not going so far as to actually rescind its earlier ratification—adopted a resolution stipulating that its approval would not extend beyond March 22, 1979. There continues to be diversity of opinion as to whether such reversals are valid; no court has ruled on the question, including the Supreme Court. But a precedent against the validity of rescission was first established during the ratification process of the 14th Amendment when Ohio and New Jersey rescinded their earlier approvals, but yet were counted as ratifying states when the 14th Amendment was ultimately proclaimed part of the Constitution in 1868.

The District of Columbia Voting Rights Amendment was proposed by the 95th Congress on August 22, 1978. Had it been ratified, it would have granted to Washington, D.C. two Senators and at least one member of the House of Representatives as though the District of Columbia were a state. Ratified by the legislatures of only 16 states—less than half of the required 38—the proposed amendment expired on August 22, 1985.

There are currently only a few proposals for amendments which have entered mainstream political debate. These include the proposed Federal Marriage Amendment, the Balanced Budget Amendment, and the Flag Desecration Amendment.