The purpose of the executive having the power to pardon is to stop judicial tyranny. It is a check on the judicature from another branch of government to stop arbitrary judicial decisions. President Bush commuting Libby's sentence was not for this purpose. it was political. There is an argument that there should be some check and balance on the executive's power in this area. (more)
Cam Riley: South Sea Republic. Freedom, liberty, equity and an Australian Republic.