A court challenge that will attempt to prove the U.S. is no longer a safe haven for refugees began Monday in Toronto, Canada.

The Third Country Agreement between the two countries stops people from crossing into Canada from the U.S., or from the U.S. into Canada and was signed 17 years ago.

But Several advocacy groups will argue in court that the Trump administration has tightened asylum rules that no longer make the U.S. a safe home for refugees and that Canada should not turn away those who try to cross into Canada from the U.S. at official

Read more: Canada court begins hearing case on asylum deal with US