Federal law explicitly bans the entry of immigrants who are "likely at any time to become a public charge," or burden to taxpayers. However, all recent presidents except for Donald Trump have not strictly enforced the law. Under guidelines issued by Bill Clinton in 1999 and left in place until 2019, federal agencies interpreted this law in a manner that ignored numerous welfare benefits, such as Medicaid, Food Stamps, Head Start, subsidized housing, and assistance with paying utility bills. In 2019, Trump issued a regulation that considered such welfare benefits when deciding whether to admit immigrants. After a series of lawsuits and injunctions by Democrat-appointed judges, higher courts allowed Trump's regulation to become nationally effective in 2020. After that, a U.S. District Court judge appointed by Barack Obama reversed the rule, Joe Biden chose not defend it, and Clinton's guidelines took effect again in 2021.