Lawyers advocating for refugee safety argued before the Canadian Supreme Court on Thursday that the U.S. is unsafe for asylum-seekers, challenging the constitutionality of the Safe Third Country Agreement.

The 2004 treaty allows the neighboring countries to share responsibility for migrants seeking asylum, obligating refugees to remain in whichever of the two nations they first enter after fleeing their homelands.

The pact is based on the assumption that the Canadian and American governments operate off of similar constitutional values of “life, liberty and security of the person” and remains in operation as long as both fulfill their obligations under international law.

“The underlying issue is whether or not the obligation to provide effective protection and to ensure effective protection is being respected by the country to which Canada is transferring refugee claimants,” said attorney Andrew J. Brouwer, advocating for refugees, according to The Washington Post.

He continued: “Our submission on the evidence is that it’s not.”

Brouwer represents three families or individuals who attempted to flee the U.S. for Canada, as well as multiple refugee advocacy organizations.

The Post reports that the appellants included an Ethiopian woman who feared that her Oromo ethnicity would subject her to persecution, a Salvadoran woman and her daughters who experienced gender-based violence and a Syrian family who fled to Canada after former President Trump issued an executive order preventing citizens of seven predominately Muslim countries, including their homeland, from entering the U.S.

The asylum-seekers and advocacy groups argue that the Safe Third Country Agreement opens Canada and the U.S. up to potential violations of the international human rights principle of non-refoulement, which protects refugees from being forcibly returned to the country that they have fled, because of the possibility that the American government would reject their settlement in the country.

Canadian government lawyer Marianne Zoric countered this idea, according to the Post, arguing that the “necessary elements of what is required for a safe third country are met in terms of international law” when it comes to the U.S.-Canada agreement.