Droit du Seigneur
Under the terms of an executive order known as droit du seigneur the President of the United States has the right to spend the first night with a newly-wedded bride.
Behind the Legend
This executive order, created in 1998 by President William Jefferson Clinton, was intended to raise the President's popularity poll numbers with American women. It has remained unchallenged, largely in part due to its "do not tell the First Lady under pain of charges of treason" clause.
Roughly a year after it was first passed, the executive order was modified to specifically exclude "brides" in same-sex marriages in which both partners are male, and to explicitly define both participants in an all-female same-sex marriage as brides.
It has been estimated that if a U.S. President ever took full advantage of the rights given by this order he would be so busy and worn out that he would have no time to legislate or do anything else, probably to the country's great benefit.