A federal judge in California on Monday dealt a setback to a new Trump administration rule that sought to block almost all asylum applications at the border, ruling that an injunction against the rule should apply nationwide.

The rule, unveiled on July 15, requires most immigrants who want asylum in the United States to first seek asylum in a third country they had traveled through on their way to the United States.

It forms part of U.S. President Donald Trump's anti-immigration policy, a centerpiece of his 2016 election campaign and a major issue as he seeks re-election in November 2020.