Under the agreement, refugee claimants must apply in the first country they arrive between the United States or Canada, unless they are entitled to a waiver. For example, asylum seekers who are citizens of a country other than the United States and who arrive from the United States at the land border between Canada and the United States can only assert their rights to refugees in Canada if they fulfill an exception under the Safe Third Country Agreement. The Safe Third Country Agreement applies to refugee claimants who wish to travel to Canada or the United States at Canada-U.S. border crossings (including rail). It also applies to airports where a person seeking protection in Country B has not been identified as a refugee in Country A and is transiting in Country A as part of his removal. The agreement helps both governments better manage access to the refugee system in each country for people crossing the land border between Canada and the United States. The two countries signed the agreement on 5 December 2002 and came into force on 29 December 2004. Conventions on safe third-country nationals are not explicitly mentioned in the 1951 Refugee Convention or the 1967 Protocol on the Status of Refugees. Rather, their legitimacy derives from Article 31 of the 1951 Convention, which states that a refugee should not be punished for illegal entry into a country if he arrives directly from a country where he is threatened.
The Office of the United Nations High Commissioner for Refugees (UNHCR) has itself warned against over-interpreting safe third country agreements, although it acknowledges that they may be acceptable in certain circumstances.  Such ambiguities have prompted some Canadian legal experts to question the legality of the Canada-U.S. safe third country agreement.  Under the agreement, refugee claimants must apply for refugee protection in the first safe country they arrive in, unless they are entitled to a waiver from the agreement. So far, the United States is the only third-country country classified as a safe third country. The Immigration and Refugee Protection Act (IRPA) requires ongoing review of all countries designated as safe third countries. The purpose of the review procedure is to ensure that the conditions that led to deportation as a safe third country remain met. On January 30, 2017, critic Jenny Kwan of the New Democratic Party (PND) of IMMIGRATION, refugees and citizens of Canada (IRCC) proposed an emergency debate on “President Trump`s immigration and travel ban from seven countries in the Middle East and North Africa.”  During the debate, the NDP called on the government to immediately suspend the agreement on the security of third-country nationals, citing the fact that “Canada can no longer trust that the U.S.
refugee system provides refuge for those at risk of persecution.”  The official Conservative Party of Canada has stated that it will not oppose the suspension of the agreement, while the Green Party of Canada has expressed support for the suspension of the agreement.  The agreement was signed on December 5, 2002 in Washington, D.C.