MLB (along with most of the other top-tier professional sports leagues) enjoys an exemption from anti-trust laws. Congress uses this as a means to investigate, meddle, and otherwise dick around.

I might be getting my facts mixed up, but a long time ago I read an article, or perhaps part of a book, that I think was written by George Will about how Congressional meddling in baseball goes back to the Black Sox scandal in 1919. Since then Congress has felt that it has a "duty" to police our national pastime.