A pocket veto is legislation passed in the last 10 days of Congress' session, which the President doesn't sign, and is therefore not enacted. The U.S. Constitution requires laws enacted by Congress must be signed into law or be vetoed by the President within 10 days. Congress must be in adjournment in order for a pocket veto to take effect. If Congress is in session and the president fails to sign the bill, it becomes law without his signature.
The U.S. Constitution Article 1, Section 7 provides: "...If any Bill shall not be returned by the President within ten Days (Sundays excepted) after it shall have been presented to him, the Same shall be a Law, in like Manner as if he had signed it, unless the Congress by their Adjournment prevent its Return, in which Case it shall not be a Law. "
