President Franklin Delano Roosevelt suspended naturalization proceedings for all German, Japanese, and Italian settlers in the United States on December 8, 1941, just one day after the Pearl Harbor attack.
Roosevelt also made clear the constitutionality of suspending naturalization proceedings from hostile nations. The Islamic State declares itself a sovereign nation.
Roosevelt issued Presidential Proclamation 2525:
Whenever there is a declared war between the United States and any foreign nation or government, or any invasion or predatory incursion is perpetrated, attempted, or threatened against the territory of the United States by any foreign nation or government, and the President makes public proclamation of the event, all natives, citizens, denizens, or subjects of the hostile nation or government, being of the age of fourteen years and upward, who shall be within the United States and not actually naturalized, shall be liable to be apprehended, restrained, secured, and removed as alien enemies…
(h/t Daniel Greenfield)