According to the US Constitution, the President, who is the head of a political party and the principal executive officer of the U.S. government, must act in accordance with the laws so as to be faithfully executed. If the President does not agree with a law it is still his or her responsibility as chief executive to abide by the laws. The US President decides how the laws of the United States are to be enforced. However, the president can veto any bill passed by Congress and the bill does not become law, except if two-thirds in each house vote to cancel the veto.