Canadas security policies have had an impact on refugee protection. Canadian judges use international law principles in refugee issues, and ensure constitutional human rights protection to everyone, including refugees and asylum-seekers. Canada has expanded the refugee definition to persons at threat of torture, according to the United Nations Convention against Torture. But, on recent security issues, Canada has had difficulty to reconcile international law and domestic law, in terms of human rights guarantees. Return to torture has been technically rendered possible by the Supreme Court of Canada, as a matter of constitutional interpretation. One particular mechanism, the security certificate, has been intensely scrutinised by courts and found wanting in many cases. The secrecy surrounding the information on which the certificate is based has been criticised, as have been the ex parte proceedings, the indefiniteness of the detention, the limitations on the role of the special advocate, and so forth. Judges have felt increasingly irritated by the intrusion of security intelligence in judicial proceedings. Canada is (now more than before) reluctant to submit to international human rights scrutiny on migration and security issues, arguing that it relates to territorial sovereignty.