_Preventive Detention_: At an early date Congress, with judicial approval, exercised the power to apprehend and detain all enemy aliens. On December 7, 1941, President Roosevelt issued the first of ten wartime proclamations founded upon Congressional enactments of 1798 and 1918, imposing limitations upon the activities of enemy aliens, and specifically announcing that “All aliens shall be liable to restraint, or to give security,”[181] and that dangerous aliens might be subjected to arrest and confinement. In two statutes enacted in 1952, Congress reiterated its desire that illegal entrants be apprehended and detained pending deportation. These statutes provided for the search of vessels and arrest of persons seeking to enter the United States illegally,[182] and authorized the establishment of necessary detention facilities to hold those arrested.[183] It is well known that in World War II persons of Japanese ancestry, including even those possessed of American citizenship, were subjected to preventive detention.[184] Presidential exercise of this form of restraint is now sanctioned on a standby basis. Title II of the Internal Security Act of 1950 empowers the President in time of “Internal Security Emergency” to order the apprehension and detention of persons “as to whom there is reasonable ground to believe that,” if free, they “will engage in, or probably will conspire with others to engage in, acts of espionage or of sabotage.”[185] The President may declare a state of internal security emergency upon the invasion of the United States or any of its territories or possessions, the declaration of war by Congress, or insurrection within the United States in aid of a foreign enemy. _Access to the U.S. and U.S. Citizenship_: Closely related to the detention of enemy aliens or others whose liberty is perceived to endanger the security of the state is the control of access to the United States and the acquisition of United States citizenship. By Act of June 20, 1941[186] Congress instructed American diplomatic and consular officers to refuse visas or entry permits to aliens believed seeking entry into the United States for the purpose of engaging in activities which would endanger the public safety. The following day Congress granted the President power during the existing national emergency to place restrictions and prohibitions in addition to those already provided by law upon the departure of persons from and their entry into the United States.[187] In proclamations of July and September 1945 and April 1946, President Truman ordered the deportation of enemy aliens resident in the United States without admission under the immigration laws, or enemy aliens deemed dangerous to the public peace and safety of the United States.[188]