Congress can override a presidential veto with a 2/3 vote of both houses. That cannot be overridden by executive power. After 10 unsigned days, excluding Sunda

Congress can override a presidential veto with a 2/3 vote of both houses. That cannot be overridden by executive power. After 10 unsigned days, excluding Sundays, bills become law, unless Congress adjourns before the 10 days expire, at which point it is automatically vetoed—the so-called “pocket veto”: http://en.wikipedia.org/wiki/Pocket_veto http://en.wikipedia.org/wiki/Pocket_veto