The Trump Administration has begun denying visas to same-sex domestic partners of foreign diplomats and UN employees.

Under the order, issued Monday, partners already in the US must get married by the end of the year or leave the country within 30 days.

The US Mission to the UN claimed that the step is necessary for international visa practices to match American policy. After the 2015 Supreme Court decision legalizing same-sex marriage, the US extends diplomatic visas only to married spouses of American diplomats.

“Consistent with [State] Department policy, partners accompanying members of permanent missions or seeking to join the same must generally be married in order to be eligible,” the Mission wrote on July 12 to UN-based delegations.

The order reverses a 2009 decision by then-Secretary of State Hillary Clinton to grant visas to domestic partners of US and foreign diplomats. Now partners of diplomats and UN officials based abroad will need to show they are married to enter the US on a diplomatic visa.

There are at least 10 UN employees in the United States who would need to get married by the New Year to have their partners’ visas extended.

Alfonso Nam, the president of UN Globe, a UN LGBTI staff advocacy organization, explained the risk to the same-sex partnerships of marriage: in some countries, they could be prosecuted.

The US told foreign governments that it will allow “limited exceptions” for countries where same-sex marriage is illegal. But the governments will have to provide documentation and commit to accepting same-sex partners of US diplomats.