Because President Obama signed it today.
On October 15, 2010, the President signed into law:
. . .
S. 3196, the “Pre-Election Presidential Transition Act of 2010,” which authorizes the General Services Administration to provide certain services and facilities prior to a general election to the principal contenders for President and Vice President of the United States for use in connection with their preparations for the assumption of official duties.
With all the media attention on disclosure, this law might be somewhat interesting because, among other things, it authorizes eligible candidates to establish a separate fund as a 501(c)(4) for costs connected to preparations for the assumption of official duties as President or Vice-President.