Federal Court Justice Ann Marie McDonald has struck down a key agreement on refugees between Canada and the United States.
She says elements of the law underpinning the Safe Third Country Agreement violate constitutional guarantees of life, liberty and security.
Canada and the U-S have recognized each other as safe places to seek protection, but Canadian refugee advocates have argued America is not always a safe country for people fleeing persecution.
They told the court that Canada is exposing ineligible refugee claimants to detention and other rights violations in returning them to the U-S.