Pregnant women visiting the US in order to take advantage of its “birthright citizenship” law to give birth to an American baby will be refused tourist visas under new rules that take effect Friday, the State Department has announced. Instead, they will be processed as foreigners seeking medical treatment - meaning they must prove they can afford not just medical care, but also the cost of living in the US while receiving it. They must also prove that the treatment they are receiving is not available where they come from.

The State Department “does not believe that visiting the United States for the primary purpose of obtaining US citizenship for a child, by giving birth in the United States…is a legitimate activity,” the agency said in a statement on Thursday, adding that the move is “necessary to enhance public safety, national security, and the integrity of our immigration system.” So-called birth tourism is a booming business, with some agencies charging as much as $80,000 for packages that include travel to and from the US with hotel stay, and has become especially popular among well-to-do Russian and Chinese women.

While anyone born in the US is guaranteed citizenship under the 14th Amendment to the Constitution, Trump has made no secret of his distaste for birthright citizenship. Banning visas for birth tourism is a much less controversial alternative to attempting to scrap birthright citizenship altogether. The president’s detractors nevertheless excoriated him for “going after pregnant women.”

Meanwhile, his supporters cheered him for taking on the thorny problem of “anchor babies” - children born in the US to foreign parents whose citizenship status is used to help relatives obtain green cards.