From Firedoglake, re: subpoenas

"Sending presidential aides up to Capitol Hill to testify will "harm the President's ability to get good information," Bush says.

Didn't seem to faze Bill Clinton:
According to the Congressional Research Service, under President Clinton, 31 of his top aides testified on 47 different occasions. The aides who testified included some of Clinton’s closest advisors:

• Harold Ickes, Assistant to the President and Deputy Chief of Staff - 7/28/94
  
• George Stephanopoulos, Senior Adviser to the President for Policy and Strategy - 8/4/94
  
• John Podesta, Assistant to the President and Staff Secretary - 8/5/94
  
• Bruce R. Lindsey, Assistant to the President and Deputy Counsel to the President - 1/16/96
  
• Samuel Berger, Assistant to the President for National Security Affairs - 9/11/97
  
• Beth Nolan, Counsel to the President - 5/4/00
  

In contrast, between 2000 and 2004, Bush allowed only one of his closest advisers, then-Assistant to the President for Homeland Security Tom Ridge, to appear in front of Congress. He has also refused three invitations from Congress for his aides to testify, a first since President Richard Nixon in 1972.

Clinton did not refuse any."

Glenn, the old lawyer himself, has more.
Kargo X has more also.