The purpose of this thesis is to examine the Canada-United States Safe Third Country Agreement. In the wake of Donald Trump's election as US president, the executive orders he has issued on matters of immigration, and various policies implemented by the administration, it is worth questioning the STCA. The STCA is an agreement between Canada and the United States which requires refugee claimants to request refugee protection in the first safe country in which they arrive in, unless they qualify for an exception to the agreement. The STCA violates both international and domestic law. Specifically, it violates the 1951 Convention Relating to the Status of Refugees and the 1967 Protocol Relating to the Status of Refugees. Domestically, it is in violation of the Canadian Charter or Rights and Freedoms. This thesis concludes that the cornerstone of the Convention, the principle of non-refoulement, has achieved the status of jus cogens.