Kathryn Steinle might be alive today if she had not lived in a “sanctuary city.”

Just 32 years old, Steinle was shot and killed nearly two years ago while strolling along San Francisco’s Pier 14. The alleged shooter was an illegal immigrant with seven felony convictions who had been deported five times. Only weeks earlier, the city had released him from custody, even though federal immigration authorities had filed a detainer requesting he be kept in custody until they could remove him for deportation proceedings. Even worse, this man admitted he came to San Francisco in part because of its sanctuary policies.

Steinle’s tragic death made the abstract debate over sanctuary cities something real for the American people. They were justifiably angry to learn that many cities and states obstruct enforcement of our immigration laws, and that this lawlessness is costing lives.

As the attorney general of the United States, I have a duty to protect public safety and uphold our nation’s rule of law. “Sanctuary city” policies harm both.

These policies take different forms. Some jurisdictions have explicit laws in place. In others, political leaders have declared they will not turn over criminal aliens in their jails to federal agents for lawful deportation or even notify federal agents that they have made an arrest — preferring instead to release aliens who have committed crimes such as domestic violence, child abuse and rape back into their communities. Others are less blatant, simply refusing to honor Immigration and Customs Enforcement detainer requests. No matter what form these policies take, they all have the same effect: They harm public safety, by putting numerous criminal aliens back on our streets. They also undermine the rule of law, by signaling that our nation’s immigration laws — laws passed by our representatives to serve our national interest — can be willfully ignored.

Supporters say “sanctuary” policies help fight crime by encouraging illegal immigrants to report crimes without fear of deportation. But how can we fight crime by allowing criminal aliens whom the law requires to be deported to stay in our country? And how does it promote the rule of law when our citizens see their leaders disregard the law?

I want San Francisco and other cities to re-evaluate these policies and recognize that we must have a lawful immigration system that keeps us safe, upholds the rule of law, and serves our national interest. The American people want, and deserve, nothing less.

Jeff Sessions is the U.S. attorney general.