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The United States Constitution vested the legislative power in the Congress.Congress can make any laws that are deemed“necessary and proper”for the federal government to apply its powers as delegated by the Constitution.It has the power to levy tax，to decide the government budget，to regulate trade，to establish and regulate a monetary system，and to borrow money on the credit of the United States.It also has the power to declare war and to raise and support armies.In addition，Congress has the power to impeach the President，Vice President，federal judges，and all other civil officers for conviction of treason，bribery，or other High Crimes and Misdemeanors.

The House of Representatives only has the power of impeaching，while the Senate only has the power to try all impeachments.State legislature also has the power to impeach state officials，including governors，based on their respective state constitution.

The U.S.Congress is composed of two houses：the Senate and the House of Representatives.The two houses are about equally important.Bills must pass both houses before being sent to the President to be signed into law.

The Senate consists of 100 members，two from each of the fifty states regardless of population.The Senators were originally chosen by the state legislatures，but they have been directly elected by voters of their respective states since 1913，in accordance with the 17th Amendment to the Constitution which took effect in that year.Senators serve for six years after they are elected，and one⁃third of the total membership of the Senate is up for election every two years.To run for the Senate，one must be at least 30 years old，has been a citizen of the United States for nine years，and be a resident of the state he or she wishes to represent.The Vice President of the United States is the President of the Senate，but he does not vote unless needed in order to break a tie.

The House of Representatives，commonly known as the House，has 435 representatives.Seats in the House of Representatives are apportioned among the 50 states according to population，but each state must have at least one seat.The whole country is divided into 435 congressional districts，and voters in each district elect one representative.House representatives serve for two years.To be a member of the House of Representatives，one must be at least 25 years old and have been a citizen of the United States for seven years.Representatives，like senators，must be residents of the state in which they are elected.The leader of the House of Representatives is the Speaker of the House，who is elected by the members of the House of Representatives.Usually，the Speaker is the leader of the majority party in the House.

The process of lawmaking starts when a member of Congress proposes a bill.Bills can originate in either house，except for bills related to budget and expenses which must originate in the House of Representatives.After a bill is proposed in the House，it is assigned to an appropriate committee for consideration.The committee refers it to a subcommittee which holds hearings on the subject.If the subcommittee approves the bill，it reports the bill back to the full committee which then considers it.If the full committee approves the bill，it would report it to the full House and put it on the House calendar for consideration.Then the full House debates the bill.During the debate，members of the House can propose changes to the bill.If the bill is passed，it goes to the Senate where it follows the same procedure.Bills originated in the Senate also have to go through the same procedure in the House.If the House and the Senate come up with two versions of the same bill，a conference committee is formed with members from both the House and the Senate to work out the differences.If they reach an agreement，then a compromise bill is sent back to the House and the Senate to be voted on.

When both houses approve the bill，then it is sent to the President of the United States.If he agrees to it，then he signs it into law.If not，he vetoes it and sends it back to Congress with a veto message explaining his reasons.If the President does not take any action on the bill within 10 days，then it automatically becomes law.However，if Congress adjourns within less than 10 days after the bill is sent to the President and the President has not signed the bill by that date，then the bill dies.This is known as a“pocket veto”，since the President can effectively quash the bill by simply keeping it in his pocket.If the President vetoes a bill but Congress is strongly in favor，it can override the veto.If more than two⁃thirds of the members in each house vote for the bill following the veto，the bill then becomes law regardless of the President’s objections.

Laws made by Congress can not violate the U.S.Constitution，which is the fundamental law of the country.Amendments can be added to the Constitution when approved by two⁃thirds of the total members of Congress and ratified approved by three⁃fourths of all the states.The Constitution has 27 amendments now，with the last one added in 1992.The first ten amendments are known as the Bill of Rights.The bill guarantees a list of citizens’rights against any governmental action，including the right to freedom of speech and religion，the right to bear arms，the right to jury trial，and the right to security of person and property.The Bill of Rights is generally considered to be the fundamental protection of Americans’rights against arbitrary government power.