Officers handling legal immigration cases will now warn people that they are under an obligation to support themselves rather than end up on the public dole, under a new policy implemented Friday by Ken Cuccinelli, acting director of U.S. Citizenship and Immigration Services.

The warning will be issued both to the immigrant and their sponsor, who under the law has signed an agreement not to let the immigrant become a public charge.

In the new warning, UCSIS officers will “remind” sponsors that they can — and now will — be asked to pay back “every dollar” of welfare that the immigrants take.

“The president has made it a priority to ensure that every individual who seeks to come to the United States is self-sufficient, temporarily or permanently,” Mr. Cuccinelli said in a memo to agency employees.

It’s the first major public move by Mr. Cuccinelli, who became acting director last week.

It’s also one of the boldest steps by the agency, which gets less attention that the Border Patrol or deportation officers, but which is nonetheless central to Mr. Trump’s immigration plans.

The president issued a memo last month urging his agencies to explore ways to make sure immigrants were living up to their terms of admission.

That immigrants are supposed to be able to support themselves has long been a part of federal policy, dating back to the very first comprehensive immigration laws enacted in the 1800s.

Today, some employment-related immigration cases and most family-based immigration cases — which account for a majority of all immigration — must be accompanied by what’s known as Form I-864, which is the affidavit of support.

As Mr. Cuccinelli explained in a tweet: “An affidavit of support is a legal and enforceable contract between the sponsor and the federal government.”

Not only is a sponsor supposed to be on the hook for costs, but an immigrant is supposed to be punished for becoming a public charge.

But it’s been rarely enforced.

The Washington Times reported in 2016 that among immigrants from five major national sources of immigration to the U.S., just three people were cited for being public charges in the years from 2013 to 2015. Immigration judges sustained just one of those cases.

Last week’s guidance is in addition to a new regulations USCIS is developing that would expand the cases where migrants could be denied immigration passes or new visas if they become a public burden.

Under Clinton-era rules, the government only looks at a narrow set of welfare programs when determining whether an immigrant has become a public charge. The Trump plan, still a work in progress, would add food stamps, public housing and long-term institutionalized care to the list.

That plan would save the government nearly $20 billion over a decade, the government argued in its draft proposal.

Immigrant-rights activists have complained that the rules would make it tougher for poor migrants to gain a foothold in the U.S., effectively giving a leg up to more successful immigrants.

Activists are already battling a new proposal by the Department of Housing and Urban Development, which would oust households led by immigrants living illegally in the U.S. from government-assisted housing. Thousands of so-called “mixed” families, where the household head is an immigrant living in the U.S. illegally but others in the home have legal status, are in government-subsidized housing.

Activists say it would punish the legal residents in those homes if they lose housing because of their relationship with an immigrant living in the U.S. illegally.