To glimpse the future of American immigration enforcement, look no further than the growing campaign against the Secure Communities program.

Under Secure Communities, federal Immigration and Customs Enforcement officials are automatically notified when an illegal alien is booked into a local jail. ICE authorities may then start deportation proceedings against the alien once he is released from jail or prison.

ICE rarely uses its power to deport illegal alien offenders: In 2012, ICE was notified of more than 400,000 jail detainees but removed only 19 percent. The removal rate was on track to be even lower in 2013. About half of those criminal illegal aliens whom ICE chooses not to deport re-offend upon release.

Yet immigrant advocates argue that the already low removal rate is far too high. They have persuaded numerous cities, counties and states to defy ICE requests to deliver illegal alien criminals to its custody after confinement, with an exception only for the most egregious cases of violent or property crime. The activists’ opposition to Secure Communities embodies the astonishing claim that someone who breaks American law by sneaking into the country illegally, and who then goes on to break other American laws, should nevertheless be exempt from deportation.

Only a few years ago, immigrant advocates protested an Arizona law, SB 1070, that encouraged state police officers to assist with federal immigration enforcement. The Obama administration joined the activists’ fight and sued Arizona for its alleged violation of federal supremacy over immigration policy. Now those same illegal alien advocates have reversed themselves and demand that states and localities defy federal authority and establish sanctuaries from federal immigration law.

The attack on Secure Communities ignores everything we have learned about criminal behavior over the past two decades. Criminals are rarely scrupulous about obeying the law; enforcing misdemeanor offenses is an effective way of incapacitating more serious criminals.

Two weeks ago, an illegal alien from Mexico went on a lethal rampage across Northern California, killing two sheriff’s deputies in cold blood and attempting to murder three other deputies as well as a civilian. Luis Enrique Monroy Bracamonte had been cited at least10 times for misdemeanor traffic violations over the previous decade, including at least one hit-and-run incident, and had been deported in 1997 and 2001 following drug and gun arrests, reentering illegally after each deportation.

Had Bracamonte been arrested for drunk driving, say, a day before his killing spree, the advocates would undoubtedly have opposed any deportation effort, on the ground that his most recent offenses were “minor.”

But even when an offender does not go on to commit more violent felonies, such allegedly “minor” offenses as shoplifting, graffiti and drug dealing create a sense of lawlessness and disorder that breaks down a community’s fabric. The argument that Secure Communities could make crime victims reluctant to cooperate with police is specious, since the program targets criminals, not victims.

The most corrosive effect of the crusade against Secure Communities, however, is simply to undermine the rule of law. Deportation is the duly enacted penalty for illegal presence. Someone who knowingly violates immigration law has assumed the risk of deportation for that offense alone. Add to that initial lawbreaking other crimes, and the illegal alien has no claim whatsoever to avoid the consequences of his behavior.

The advocates’ ultimate goal is to delegitimize deportation entirely as a response to illegal immigration. Never mind that other countries, including Mexico, routinely remove illegal immigrants. If someone cannot be removed for illegal entry, national sovereignty becomes meaningless, and immigration laws, a nullity. Should the advocates succeed in their mission, the United States will have formally ceded control of its immigration policy to people living outside its borders.

Heather Mac Donald is Thomas W. Smith fellow at the Manhattan Institute and a contributing editor of City Journal magazine.