Based on the tapes from the oval office, Richard Nixon felt that because he was president that he was above the law. This meant that the normal laws of the Untied States did not necessarily apply to him.
However, this was not the reality of the situation. In the Supreme Court case Nixon vs. United States, the Supreme Court ruled overwhelmingly that Nixon was not above the law and had to hand over the tapes to the court. This ultimately resulted in the resignation of Nixon.