Constitution? What Constitution?

I just watched some of the testimony of Tim Geithner and Ben Bernake to a congressional panel that troubled me greatly. Geithner was asked my a congresswoman under what constitutional authority he had to expand the powers of the Treasury department. Geithner's answer was that he was given the authority to do so by the Congress.

But that wasn't the question.

The question was what CONSTITUTIONAL authority (since we are a nation ruled by law not by consensus) not Congressional authority gave him the power to expand the powers of the government. He kept responding to the question by saying that his authority was granted by Congress.

The problem is that...how far could this go? Does this mean that if the Congress decides to give the Federal Govt power over all private industry, that they can do that? If Congress decides to ban all guns except by the military, can they do that? If Congress decides that Communism is a better way for us to handle our country's future, they can do that?

According to Mr. Geithner, since the Constitution isn't relevant for what the government can or cannot do, then these, as well as other anti-freedom decisions are definitely plausible as a part of our future as a country.