The basic principle is straightforward.

If you make it to the border of a foreign country, you have a right to request asylum. That country is obligated to hear and evaluate your claim. It cannot kick you out while it’s processing you — which can take months or years — or if you face a credible threat of persecution at home. If the country finds you meet the definition of a refugee, it is obligated to shelter you. If you don’t, only then can it expel you.

These rights came out of World War II, which created huge numbers of refugees in Europe. The war’s victors spent much of the next decade setting up what became the international order, enshrined in laws that regulate things like warfare or that establish universal rights.

Protection for refugees made the list because it was an urgent issue at the time and because it was seen as a way to uphold stability and basic rights amid any future humanitarian crises.

And after the United States and others had turned away Jewish refugees during the Holocaust, the world felt compelled to promise “never again.”

Refugees’ rights became enshrined in international law through global agreements signed in 1951 and again in 1967, when the end of colonialism brought more crises.

Not all countries signed these pacts; the United States ratified only the 1967 agreement and several Middle Eastern and Asian countries signed neither. But they are considered to be to be so widely agreed upon that they constrain everyone.

Still, what makes asylum one of the world’s strongest norms is that it is written into the domestic laws of many countries, including the United States. After all, asylum is administered by domestic governments and courts.