[Dan Evans]

The international free market in currency establishes the value of the dollar. No one controls it.

[JohnSmithee]

"The international free market in currency establishes the value of the dollar. No one controls it."

That may be true, but it doesn't mean that it can't be influenced.

[JohnSmithee]

"The international free market in currency establishes the value of the dollar. No one controls it."

The important factor is the value of the dollar relative to other currencies such as the Yuan, which is pegged to the value of the dollar.

[Celtman]

The international free market in currency establishes the value of the dollar. No one controls it.

"The Congress shall have Power... To coin Money, regulate the Value thereof, and of foreign Coin"

Constitution of the United States

Congress has unwisely chosen to ignore this power.  The "international free market" is manipulated by the IMF and the Federal Reserve Board to such a degree that the freedom of the market is a myth, except within narrow bounds.