The last time the nation’s immigration law was overhauled, it was widely reported that Democrats had won the fight because the Republican-controlled Congress backed away from its most onerous proposals.

President Bill Clinton signed the Illegal Immigration Reform and Responsibility Act the month before his 1996 re-election victory over Senate Majority Leader Bob Dole. Like House Speaker Newt Gingrich, Dole had been pushing for such tough provisions as allowing states to bar unauthorized-immigrant children from public schools. The bill passed without that measure, leading Clinton to declare that the law was being strengthened “without hurting innocent children or punishing legal immigrants.”

Not so. The 1996 law has proven to be a civil-liberties nightmare by requiring mandatory detention, often without a bond hearing, for non-citizens (including those in the country legally) convicted of a wide range of crimes. Many of those detained—more than a quarter-million people since 2000—are ultimately found eligible to remain in the United States. Some 17,268 of them had been in the country for 20 or more years when they were arrested and jailed, according to federal data made available by the Transactional Records Access Clearinghouse at Syracuse University. In hundreds of cases, people who actually were American citizens were mistakenly detained as illegal immigrants, according to the Deportation Research Clinic at Northwestern University.

One little-noticed aspect of the law: It allocated $12 million to build a fence along the border near San Diego.

The 1996 law was no defeat for the nativism that was building in the House Republican caucus, following on California voters’ approval of the anti-immigrant Proposition 187 in 1994. It allowed for mass incarceration of immigrants—which Republicans in Congress later enhanced with a measure that forced the government to maintain at least 34,000 immigration detention beds, whether they were needed or not.

As Congress looks to overhaul immigration law anew, the discussion is not about how to end the injustices the 1996 law has caused while better securing the borders. With the exception of finding a path for the young immigrants protected under President Barack Obama’s Deferred Action for Childhood Arrivals order, it’s about making that law tougher.