The Trump administration is cracking down on American citizens who sponsor immigrants that become a strain on the U.S. welfare system.

American sponsors are legally liable for the welfare benefits received by immigrants they sponsor. The laws, part of the Personal Responsibility and Work Opportunity Act of 1996, have rarely been enforced, however.

"The immigration laws currently require that, when an alien receives certain forms of means-tested public benefits, the government or non-government entity providing the public benefit must request reimbursement from the alien’s financial sponsor," a Thursday memo signed by President Trump says.

"Agencies are not adequately enforcing these requirements," the memo says. "Ensuring compliance with the rule of law requires renewed efforts to enforce these requirements and the issuance of appropriate guidance so agency practices and enforcement can be aligned with Federal law."

Under the administration’s new policies, state agencies must provide the names of immigrants receiving public benefits to the federal government. The Treasury Department will then bill the immigrants’ sponsors. If the bill is not paid, the department will withhold the amount from the sponsor’s tax returns.

[ Opinion: I'm an immigrant Republican. Democrats need to get on board with Trump's immigration plan]