A veto gives power, possibly unlimited, to stop changes, but not to adopt them. The influence that the veto conveys to its holder is therefore directly proportional to the holder's conservatism, broadly defined. The more the holder of a veto supports the status quo, the more useful the veto.
The concept of a veto body originated with the Roman consuls and tribunes. Either of the two consuls holding office in a given year could block a military or civil decision by the other; any tribune had the power to unilaterally refuse legislation passed by the Roman Senate.
In the United Nations Security Council, the five permanent members (the United States, Russia, the People's Republic of China, France and the United Kingdom) have veto power in substantive matters, though not in procedural ones. If any of these countries votes against a proposal, it is rejected, even if all of the other member countries vote in favour.
The word "veto" does not appear in the United States Constitution. Per U.S. Const., Article I, Section 7 all legislation passed by both houses of Congress must be presented to the President. This presentation is in the President's capacity as head of state.
If the President approves of the legislation, he signs it (sign into law). If he does not approve, he must return the bill, unsigned, within ten days, excluding Sundays, to the house of the United States Congress in which it originated, while the Congress is in session. The President is constitutionally required to state his objections to the legislation in writing, and the Congress is constitutionally required to consider them, and to reconsider the legislation. This action, in effect, is a veto.
If the Congress overrides the veto by a two-thirds majority in each house, it becomes law without the President's signature. Otherwise, the bill fails to become law unless it is presented to the President again and he chooses to sign it.
A bill can also become law without the President's signature if, after it is presented to him, he simply fails to sign it within the ten days noted. If there are fewer than ten days left in the session before Congress adjourns, and if Congress does so adjourn before the ten days have expired in which the President might sign the bill, then the bill fails to become law. This procedure, when used as a formal device, is called a pocket veto.
In 1996, the Congress passed, and President Bill Clinton signed, the Line Item Veto Act of 1996. This act allowed the President to veto individual items of budgeted expenditures from appropriations bills instead of vetoing the entire bill and sending it back to the Congress. However, this line-item veto was immediately challenged by members of Congress who disagreed with it. In 1998, the Supreme Court declared that the line-item veto was unconstitutional. The Court found the language of the Constitution required each bill presented to the President to be either approved or rejected as a whole. An action by which the President might pick and choose which parts of the bill to approve or not approve amounted to the President acting as a legislator instead of an executive and head of state - and particularly as a single legislator acting in place of the entire Congress - thereby violating the separation of powers doctrine. (See Clinton v. City of New York, .)
In 2006, Senator Bill Frist introduced the Legislative Line Item Veto Act of 2006 in the United States Senate. Rather than provide for an actual legislative veto, however, the procedure created by the Act provides that, if the President should recommend rescission of a budgetary line item from a budget bill he previously signed into law - a power he already possesses pursuant to U.S. Const. Art. II - the Congress must vote on his request within ten days. Insomuch as the legislation that is the question of the President's request (or "Special Message", in the language of the bill) was already enacted and signed into law, either by this president or a prior president, any action by the Congress would be ordinary legislative action, not any kind of veto - whether line-item, legislative or any other sort. The House passed this measure, but the Senate never considered it, so the bill expired and never became law.
In 1982, the Supreme Court had struck down the one-house legislative veto, also on separation of powers grounds and on grounds that the action by one house of Congress violated the Constitutional requirement of bicameralism. The case was INS v. Chadha, concerning a foreign exchange student in Ohio who had been born in Kenya but whose parents were from India. Because he was not born in India, he was not an Indian citizen. Because his parents were not Kenyan citizens, he was not Kenyan. Thus, he had nowhere to go when his student visa expired because neither country would take him, so he overstayed his visa and was ordered to show cause why he should not be deported from the United States.
The Immigration and Nationality Act was one of many acts of Congress passed since the 1930s, which contained a provision allowing either house of that legislature to nullify decisions of agencies in the executive branch simply by passing a resolution. In this case, Chadha's deportation was suspended and the House of Representatives passed a resolution overturning the suspension, so that the deportation proceedings would continue. This, the Court held, amounted to the House of Representatives passing legislation without the concurrence of the Senate, and without presenting the legislation to the President for consideration and approval (or veto). Thus, the Constitutional principle of bicameralism and the separation of powers doctrine were disregarded in this case, and this legislative veto of executive decisions was struck down.
The Presidents of the Continental Congress (1774 - 1781) did not have the power of veto. Nor could the President veto an act of Congress under the Articles of Confederation (1781 - 1789), though he possessed certain recess and reserve powers that were not necessarily available to the predecessor President of Continental Congress. But with the enactment of the United States Constitution (drafted 1787; ratified 1788; fully effective since 4 March 1789), veto power was conferred upon the person titled "President of the United States."
The presidential veto power was first exercised on April 5, 1792 when George Washington vetoed a bill designed to apportion representatives among the several states. The Congress first overrode a presidential veto - that is, passed a bill into law notwithstanding the President's objections - on March 3, 1845.
Most U.S. states also have a provision by which legislative decisions can be vetoed by the governor. In addition, most of these states allow the governor to exercise a line-item veto.