Italian American internment refers to the internment of Italian Americans in the United States during World War II.
The term "Italian American" does not have a legal definition. It is generally understood to mean ethnic Italians of American nationality, whether Italian-born immigrants to the United States (naturalized or unnaturalized) or American-born people of Italian descent (natural-born U.S. citizens).
The term "enemy alien" has a legal definition. The relevant federal statutes in Chapter 3 of Title 50 of the United States Code, for example par. 21 which applies only to persons 14 years of age or older who are within the United States and not naturalized. Under this provision, which was first defined and enacted in 1798 (in the Alien Enemies Act, one of the four Alien and Sedition Acts) and amended in 1918 (in the Sedition Act of 1918) to apply to females as well as to males, all "...natives, citizens, denizens or subjects..." of any foreign nation or government with which the United States is at war "...are liable to be apprehended, restrained, secured and removed as alien enemies...."
Thus, at the outbreak of World War II, for example, an Italian businessman temporarily living in the United States, Italian diplomats, and Italian international students studying in the United States all became "enemy aliens" the moment Italy declared war on the United States. In some cases, such temporary residents were expelled (such as diplomats) or given a chance to leave the country when war was declared. Some were interned, as were the Italian merchant seamen caught in U.S. ports when their ships were impounded (discussed below) in 1939 when war broke out in Europe.
The members of the "Italian community" in the United States presented an unusual problem. Defined in terms of national origin, it was the largest community in the United States, having been supplied by a steady flow of immigrants from Italy between the 1880s and 1930. By 1940, there were, thus, millions of native-born Italian Americans in the United States. However, there were also a great many Italian "enemy aliens" (more than 600,000, according to most sources). These were not Italian students, diplomats, or businessmen, but rather 600,000 Italians who had immigrated during the previous decades and had never become naturalized citizens of the United States.
The laws regarding "enemy aliens" did not make ideological distinctions—treating as legally the same pro-Fascist Italian businessmen living for a short time in the U.S. and trapped there when war broke out, anti-Fascist refugees from Italy who arrived a few years earlier intending to become U.S. citizens but who had not completed the process of naturalization, and those who had emigrated from Italy at the turn of the century and raised entire families of native-born Italian Americans but who were not naturalized themselves. They were all considered enemy aliens.
The problem of "enemy aliens" in the U.S. started well before the nation's entry into World War II on December 8, 1941, immediately following the attack on Pearl Harbor. In September, 1939, when Britain and France declared war against the Axis nations of Germany and Italy (later to include Japan), President Franklin D. Roosevelt authorized the Director of the Federal Bureau of Investigation, J. Edgar Hoover, to compile a Custodial Detention Index of persons to be arrested in case of national emergency. Thus, at least a year before Pearl Harbor, the Department of Justice began to list possible saboteurs and enemy agents among the German, Japanese and Italian populations.  Also, resident aliens were registered in 1940 under the Smith Act.
A distinction must be made between:
Generally speaking, that was not the case with members of the Italian community. Although there were anomalous cases of U.S. native-born Italian Americans being caught in the round-up, the others had been born in Italy and were still Italian citizens, even if many of them had resided in the U.S. for decades.
Di Stasi cites a number of such cases of mistreatment and internment of "Italian Americans," although he apparently defines "Italian American" as anyone within the Italian community, native-born US citizens or Italian-born non-US citizens.
The general chronology of events regarding the treatment of enemy aliens and the reaction in the Italian community is as follows:
Hundreds of Italians were arrested in the months immediately after Pearl Harbor. By June 1942, the total reached 1,521 Italian aliens arrested by the FBI. About 250 individuals were interned for up to two years in military camps in Montana, Oklahoma, Tennessee, and Texas.
Italy's surrender on September 8, 1943 brought about the release of most of the Italian American internees by year's end. Some had been paroled months after "exoneration" by a second hearing board appealed for by their families. Nonetheless, most of the men had spent two years as prisoners, moving from camp to camp every three to four months.