The learned professor makes the same mistake that everyone makes when discussing the office of Attorney General:  claiming that the AG is the "chief law enforcement officer of the United States."  He is not.  In fact, the office of AG does not exist anywhere in the Constitution.  The office of President is the chief law enforcement officer of the United States, and all in the Executive branch are subordinate to him/her.  As such, I would think that the President does indeed have the right to expect loyalty from his/her attorney general.  A better solution than the one that Professor Dershowitz proposes would be to tightly circumscribe the performance of any special counsels appointed to independently investigate Executive branch malfeasance.  Tightening up the scope of independent counsel investigations, limiting them strictly to the issue they were in fact appointed to investigate, rather than the fishing expeditions they routinely become, would go much farther in this regard.