1210 GMT November 12, 2019
The policy, enacted by Trump last year, is among a host of measures his government has taken against the movement of hundreds of thousands of migrants from Central America and elsewhere who have recently tried to cross into the US from Mexico and request asylum, AFP reported.
Federal judge Randolph Moss, sitting in Washington, ruled that the policy was "in excess of statutory... authority," ABC News reported.
Moss said it contradicts standing US immigration law, which allows undocumented people who are physically present in the country to apply for asylum even if they did not enter at an official port of entry, The Hill newspaper said.
The policy had earlier been blocked by a judge in San Francisco, a ruling the government is appealing.
Trump's immigration policy has been the subject of numerous court challenges.
Last week, a federal judge in California issued a preliminary injunction blocking the administration's new rule barring most immigrants from obtaining asylum in the US if they transit through Mexico.
That policy would have effectively prevented most Central American asylum seekers from gaining entry into the United States at the southern border, as the majority come through Mexico.
Day later, Guatemala signed an agreement with the US that, according to Washington, makes it a "safe third country," meaning migrants who want to seek asylum in the United States but travel through Guatemala must request asylum in the Central American country.
The number of border-crossers detained by the US Border Patrol surged to a 13-year high of more than 144,000 in May before easing to 104,000 in June – still up 142 percent from a year earlier.
Most are families from Guatemala, Honduras and El Salvador.