Article II, Section 2 of the U.S. Constitution says, "[The President] shall have Power to Grant Reprieves and Pardons for Offenses against the United States, except in Cases of Impeachment."
I propose amending the Constitution to ban pardons in which the President of the United States has a conflict of interest. The President should not be able to pardon his co-conspirators, like Caspar Weinberger (Bush 41 pardoned Weinberger for his role in Iran-Contra) or "Scooter" Libby, and s/he should not be able to pardon major campaign contributors or "friends of the party" like Marc Rich and George Steinbrenner (pardoned by Reagan for illegal campaign contributions to Nixon).
See the amendment after the jump.
Proposed Amendment 28:
Section 1. No pardon shall be granted in cases where the President has a conflict of interest with either the crime or the individual. Conflict of interest pardons granted before ratification of this amendment shall be invalidated if the statute of limitations has not expired.
Section 2. No pardon shall be granted between election day and inauguration except for individuals who have completed incarceration and paid fines as directed by the courts.
Section 3. In cases where the President has granted a pardon, a prosecutor with jurisdiction may apply to the federal courts for the pardon to be invalidated based on the conflict of interest. In cases of impeachment the House of Representatives shall apply to the Supreme Court
In my discussions about an amendment banning conflict-of-interest pardons politburo suggested banning late term pardons and my father made a distinction between pardons for people who have been punished and those who have not been tried yet.
Outside of the specific issue of "Scooter" Libby, it's just wrong for the President to sell pardons or to pardon his co-conspirators in criminal activity.