USAJOBS | Employment of non-citizens
Snippet of Article: "In general, you must be a U.S. citizen or national (residents of American Samoa and Swains Island) to work for the federal government, but there are some exceptions. In rare cases, a federal agency may:
* Hire a non-U.S. citizen into the excepted service or Senior Executive Service, if the annual Appropriations Act, the Immigration Law and the agency’s internal policies allow it.
* Request approval to hire a non-U.S. citizen into the competitive service, if no qualified U.S. citizen is available. "