The Safe Third Country Agreement (STCA) is a bilateral agreement between Canada and the United States that was signed in 2002. Its purpose is to ensure that refugees and asylum seekers have access to safe and fair refugee protection.

The STCA is based on the principle that individuals seeking asylum should claim asylum in the first safe country they reach. This means that if someone arrives at the Canadian border from the US and has already made a claim for refugee protection in the US, they will be turned away by Canadian border officials and told to return to the US.

The rationale behind this agreement is that both countries are considered to be safe countries for refugees and asylum seekers. The US and Canada have comprehensive systems in place to handle refugee claims and offer protection to those who need it.

The STCA applies to all individuals who arrive at a land border crossing between Canada and the US. It does not apply to individuals who arrive in Canada by air or sea, or to people who have been in transit through the US to reach Canada.

The STCA has been controversial, and there have been legal challenges mounted against it. Critics argue that the US is not a safe country for refugees and asylum seekers, particularly under the current administration. There are concerns about the treatment of migrants and the conditions in detention centres.

In 2017, the Canadian Council for Refugees launched a legal challenge against the STCA, arguing that it violates the Canadian Charter of Rights and Freedoms. They argue that the US is not a safe country for refugees and asylum seekers, and that Canada is complicit in sending them back to a country where they may face persecution or harm.

The outcome of the legal challenge is yet to be determined. However, the STCA remains in effect, and individuals who arrive at a land border crossing between Canada and the US will continue to be subject to its provisions.

In conclusion, the Safe Third Country Agreement is a bilateral agreement between the US and Canada that is meant to ensure that refugees and asylum seekers have access to safe and fair refugee protection. However, the agreement has been controversial, with critics arguing that the US is not a safe country for refugees and asylum seekers. Legal challenges are ongoing, and the outcome remains to be seen.