Presidential Memoranda: Similar to executive orders, presidential memoranda are written instructions from the President to executive branch officials that carry the force of law, but are not published in the Federal Register like executive orders.
Signing Statements: Statements issued by the President upon signing a bill into law, which can be used to provide the President's interpretation of the legislation or to assert the President's constitutional powers.
Unitary Executive Theory: The idea that the President, as the head of the executive branch, has complete control over the entire executive branch and can direct the actions of all executive officials.