It seems like at least parts of the government argue that any government copying is inherently fair use http://www.loc.gov/flicc/gc/fairuse.html

Fun fact, the government opinion for patents for the government and its contractors is also that the federal government cannot be found to infringe on patents either. At most they say they voluntarily choose to provide reasonable compensation. This especially applies if the use of a patent is deemed to be in the interest of national security.