Orin Kerr argues that Congress can force the Supreme Court to televise its oral arguments. I agree. The law would be necessary and proper to carrying into executive the judicial power. In addition to the arguments that Orin makes, I would think the law would be similar to the laws requiring that certain executive advisory committees (FACA) and certain executive documents (FOIA) be open to the public.
While I am not certain that televised proceedings would be a good idea, I think that there is a strong presumption in favor of such open proceedings (that is not overcome) and therefore support televising them.