Newsweek's Michael Isikoff reports that just a few days before leaving the White House, President George W. Bush sent a very interesting letter to former aide Karl Rove:
On Jan. 16, 2009, then White House Counsel Fred Fielding sent a letter (.pdf) to Rove's lawyer, Robert Luskin. The message: should his client receive any future subpoenas, Rove "should not appear before Congress" or turn over any documents relating to his time in the White House. The letter told Rove that President Bush was continuing to assert executive privilege over any testimony by Rove—even after he leaves office.
Here's Yale law professor Jack Balkin's response:
The fact that Bush sent these letters while he was still president makes no difference. He is no longer president. The claim of absolute immunity he is making (as opposed to executive privilege, which is not absolute) would be controversial even if offered by a sitting president, but it is even more so when offered by a former president.
Radley Balko explains why Barack Obama should swear off executive privilege here.