According to this Variety article, the original deal with Spike TV was made back in 2005. They paid $65 million for the exclusive broadcast rights for all six movies for six years starting in 2008. This deal was exclusive; the only way you were watching Star Wars on basic cable in the US was on Spike.
Before that Fox's own TV network had the rights. They even paid $80 million for a 10-year exclusive license for The Phantom Menace. *sad trombone*
Six years after 2008 is 2014. January 2014 is the last time I can find Spike TV did a Star Wars marathon and they did this awesome commercial starring the 501st Legion.
According to this Hollywood Reporter article, Fox, not Disney, still owns the rights to broadcast the six Star Wars movies, while Disney has the rights to digital distribution.
The five most recent revert to Disney in 2020, but Fox holds onto A New Hope forever. Here's the relevant quote (the "third-party studio" is Fox):
Prior to the Company’s acquisition, Lucasfilm produced six Star Wars films (Episodes 1 through 6). Lucasfilm retained the rights to consumer products related to all of the films and the rights related to television and electronic distribution formats for all of the films, with the exception of the rights for Episode 4, which are owned by a third-party studio. All of the films are distributed by a third-party studio in the theatrical and home video markets. The theatrical and home video distribution rights for these films revert back to Lucasfilm in May 2020 with the exception of Episode 4, for which these distribution rights are retained in perpetuity by the third-party studio.
—"Fiscal Year 2013 Annual Financial Report And Shareholder Letter", page 13, The Walt Disney Company
It's Fox, not Disney, who controls who gets to broadcast Star Wars.
I can't find information on who currently has broadcast rights in the US. Likely they're holding it back until the release of the new movie.