The term aggravated felony was created by the United States Congress as part of the Immigration and Nationality Act (INA) to define a special category of criminal offenses. The INA says that certain aliens "convicted of an aggravated felony shall be considered to have been convicted of a particularly serious crime." Every "legal immigrant," including a "national but not a citizen of the United States," who has been convicted of any aggravated felony is ineligible for citizenship of the United States, and other than a refugee, every alien who has been convicted of any aggravated felony is ineligible to receive a visa or be admitted to the United States, if his or her "term of imprisonment was completed "within" the previous 15 years."