Baseball & Government

Can someone please show me where in the Constitution it says that Congress can regulate Major League Baseball? I’ve been looking and I’ve yet to find it. Did they write it in invisable ink? You can’t find it because it doesn’t exist. The federal government has no business involving it’s self in professional baseball or any other sport.
Once again, the MLB and the government should let the free market play it’s role here. If baseball doesn’t straighten out on steroids, fans will stop coming to games. It’s happened before, like in 1994 and 1995 when the MLBPA went on strike.
However, people like Senator John McCain and Congressman Tom Davis (R-VA) don’t understand their limited powers under the Constitution, a document they’ve either never read or ignore. Yet McCain, Davis and others keep throwing whatever power they think they have at Major League Baseball by threatening federal legislation on the steroid issue.
When will they learn?