The 9th U.S. Circuit Court of Appeals had said the government could enforce the policy everywhere but in California and Arizona, states covered by the 9th Circuit. The Justice Department calls the order now in effect "deeply flawed."
The policy would deny asylum to anyone who passes through another country on the way to the U.S. without seeking protection there. Most people crossing the southern border are Central Americans fleeing violence and poverty. They'd largely be ineligible.