Toronto schools will no longer allow student or staff trips to the U.S. due to uncertainty over whether everyone will be allowed to enter in the wake of President Trump’s travel ban.

In a statement released Thursday, John Mallow, direct of education for the Toronto District School Board (TDSB), said that already-approved trips to the U.S. would still be allowed to proceed, so long as the travel ban is not fully implemented.

No new school travel will be allowed at this time. And if the travel ban is fully implemented, even already-approved trips will be called off.

“We do not make this decision lightly, but given the uncertainty of these new travel restrictions and when they may come into effect, if at all, we strongly believe that our students should not be placed into these situations of potentially being turned away at the border,” Malloy said.

The TDSB isn’t the first such group to issue a halt on travel to the U.S. as a result of Trump’s executive order. The Girl Guides of Canada, the country’s version of the Girl Scouts, announced that they are refusing to approve members’ trips to the U.S., saying that “the ability of all our members to equally enter this country is currently uncertain.”

Trump signed his original travel ban on Jan. 27, which barred citizens of seven Muslim-majority countries — Syria, Iraq, Iran, Yemen, Libya, Sudan and Somalia — from entering the U.S. He issued a revised order earlier this month, which removed Iraq from the list, among other things, after the initial ban was blocked in federal court. The new order has since been blocked by a federal judge in Hawaii.

Still, Trump has vowed to appeal the judge’s ruling up to the Supreme Court, arguing that the travel ban falls well within his power as president.