A blurb from the wiki on Veto Powers

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. 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. 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.
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.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.

Since Luke is technically the President (He chose this book) we can overide his NAY with a 2/3 majority vote. We have laws from which can draw power or that can screw us over.