The government indirectly regulates exchange rates, because most currency exchange rates are set on the open foreign exchange market (forex). In some countries, like China, the exchange rate is fixed, and the government directly controls it. This control of the yuan, in turn, affects the U.S. dollar. The yuan is loosely pegged to the U.S. dollar.
The U.S. government has various tools to influence the U.S. dollar exchange rate against foreign currencies. The nation's central bank—known as the Federal Reserve (Fed)—is an independent arm of the government. It indirectly changes exchange rates when it raises or lowers the fed funds rate—the rate banks charge to lend to each other.
For example, if the Fed lowers the rate, this drives down interest rates throughout the U.S. banking system and increases the supply of money, which tends to weaken the dollar relative to other currencies, given the anticipated inflationary pressure. The diminished rates also tend to weaken demand for dollar-denominated assets, which can have a knock-on effect on the value of the currency.
Treasury Department Role
The Treasury Department is a government agency that also indirectly affects the exchange rate. It prints more money. This printing increases the supply and weakens the dollar. It can also borrow more money from other countries. That's done by selling Treasury notes, which increases the supply of money and increases the U.S. debt, and both will send the dollar's value down.
The third government tool is the use of expansionary fiscal policies. Generally, these policies weaken the dollar, because they increase the supply of money. However, these policies can also improve economic growth, which tends to attract domestic and foreign investors to dollar-denominated assets. This demand can often overshadow the expansion in the supply of dollars.
The chart below shows the Trade Weighted U.S. Dollar Index from 2000 through today:
Regulations on Foreign Exchange Trading
The Chicago Futures Trading Commission regulates forex brokers. It oversees all U.S. forex brokerage companies, enforces its regulations, and prosecutes outright fraud. Its authority was strengthened in 2010 with the Dodd-Frank Wall Street Reform Act.
Approximately 95% of the $5.1 trillion traded daily on forex markets changes hands via spot currency transactions rather than futures transactions. Since these consist of two-day delivery rather than cash, they are considered the same as futures contracts. For this reason, a broker must register as a commodity trading advisor, a futures commission merchant, an introducing broker, or a commodity pool operator with the Commodity Futures Trading Commission and become a member of the National Futures Association.
The U.S. National Futures Association (NFA) is a self-regulating association. All U.S. forex brokers operating on behalf of other U.S. clients must register. The NFA’s objective is to protect the integrity of U.S. markets and to protect investors from fraud, but the association doesn't get involved with the value of any particular currency.
The U.S. Treasury Department is always on the lookout for any price-fixing in forex trading.