_Circumscribing Movement of Persons_: The area of permissible mobility is narrowed for all persons in time of war or emergency. The population generally is excluded from specified security areas. By Act of January, 1938,[198] Congress authorized the President to define certain vital military and naval installations or equipment and made it unlawful to photograph or sketch such installations without proper authority. This obviously limits access to and activity in areas adjacent to such equipment. A 1950 amendment to the Civil Aeronautics Act, for example, empowered the Secretary of Commerce, after consultation with the Department of Defense and the Civil Aeronautics Board, to define zones or areas in the airspace above the United States, its Territories, and possessions as he may find necessary in the interests of national security. The Secretary is also given authority to prohibit or restrict flights of aircraft which he cannot effectively identify, locate, and control in those areas.[199] Selected groups of persons, generally enemy aliens, may be prohibited from entering or remaining in certain areas of the country. Proclamation No. 2525, December 7, 1941,[200] forbade the presence of alien Japanese in the Canal Zone, and restricted their entry into, or departure from, Hawaii, the Philippine Islands, and the United States, and provided for their exclusion from designated areas. Of maximum severity were limitations on mobility beyond the limits of a community, or confinement in a camp or cell. The movement to restrict travel by Americans dates from the 1935 endeavor of the American Congress to avoid American involvement in any future conflict. Section 6 of the Neutrality Act of 1935[201] empowered the President to prohibit or regulate travel by American citizens as passengers on the vessels of any belligerents in a war in which the United States was a neutral. Individuals travelling in violation of orders did so at their own risk. Two months after passage of the Neutrality Act, in October 1935, President Roosevelt issued Proclamation No. 2142, applying Section 6 to the Ethiopian conflict, and ordering American citizens to refrain from traveling as passengers on vessels of either belligerent. The May 1937 amendments to the Neutrality Act[202] strengthened this provision by making it unlawful for any United States citizen to travel on belligerent vessels in contravention of the President’s prohibition or regulation of such travel. In 1939 these provisions were broadened to include any American travelling on such a vessel as a member of its crew,[203] and to prohibit American ships from carrying goods or passengers to belligerent ports[204] or combat areas.