In 1986, America had an estimated population of three to five million illegal immigrants. That year, as part of the most sweeping change in immigration law in thirty-four years, Congress took the controversial step of reducing the number of illegal immigrants by legalizing them. Under Section 245A of the Immigration Reform and Control Act (IRCA), illegal aliens who had resided in the United States since before 1982 could apply for temporary or permanent residence. Approximately three million applications for legalization were processed by the Immigration and Naturalization Service (INS) within the next several years; 88 percent were admitted as permanent legal residents.

Amnesty (legal forgiveness) for illegal immigrants was criticized when it was first enacted, and whether to extend it to more recently-arrived immigrants is a source of debate to this day. The fundamental objection, as John Tanton argued before a Senate committee in...