the president has 4 options when signing a bill which are :1) To sign it - becomes a law 2) To veto it - refuse to sign it, must be returned to original house with a veto message 3) To allow the bill to become a law without signing - not acting on it for 10 days 4) Pocket Veto - If congress adjours its session within 10 days of submitting and the president does not act, the measure dies.
If a bill has passed in both the U.S. House of Representatives and the U.S. Senate and has been approved by the President, or if a presidential veto has been overridden, the bill becomes a law and is enforced by the government.