By what legal right?
 
On December 3, 2008, Obama was/is a private citizen. He resigned his U.S. Senate seat on Nov. 13th.
 
https://www.washingtonpost.com/wp-dyn/content/article/2008/12/02/AR2008120203489_pf.html

"Wearing yellow badges and traveling in groups of 10 or more, agency review teams for President-elect Barack Obama have swarmed into dozens of government offices, from the Pentagon to the National Council on Disability.

"With pointed questions and clear ground rules, they are dissecting agency initiatives, poring over budgets and unearthing documents that may prove crucial as a new Democratic president assumes control. Their job is to minimize the natural tension between incoming and outgoing administrations, but their work also is creating anxiety among some Bush administration officials as the teams rigorously examine programs and policies."