A U.S. judge in New Mexico on Thursday dismissed trespassing charges against dozens of migrants caught in a new military zone on the U.S.-Mexico border, marking a setback for Trump administration efforts to raise penalties for illegal crossings.

The magistrate ruled that apprehended migrants may not have been aware they were crossing into a military zone.

A federal judge found no probable cause to believe that the migrants knew they were entering a military zone and thus “willfully” trespassed onto land the Trump administration declared “national security areas” earlier this month.