<P> One of the foremost non-legislative functions of the Congress is the power to investigate and to oversee the executive branch . Congressional oversight is usually delegated to committees and is facilitated by Congress' subpoena power . Some critics have charged that Congress has in some instances failed to do an adequate job of overseeing the other branches of government . In the Valerie Plame Wilson episode sometimes known as the Plame affair, some critics, including Representative Henry A. Waxman, charged that Congress was not doing an adequate job of oversight in this case . Other critics charge Congress was lax in its oversight duties regarding presidential actions such as warrantless wiretapping, although others respond that Congress did investigate the legality of decisions by President George W. Bush involving such matters . </P> <P> Congress also has the exclusive impeachment power, allowing impeachment, trial, and removal of the President, federal judges and other federal officers . </P> <P> Among the powers specifically given to Congress in Article I Section 8, are the following: </P> <P> 1.To lay and collect taxes, duties, imposts and excises, to pay the debts and provide for the common defense and general welfare of the United States; but all duties, imposts and excises shall be uniform throughout the United States; </P>

What is the main duty of the u.s. congress