Santa Fe, 16 May

Federal magistrate judges in New Mexico have started dismissing national security charges against immigrants accused of crossing the southern US border through a newly designated military zone, finding little evidence that immigrants knew about the zones.

Since late-April, federal prosecutors in New Mexico and western Texas have filed misdemeanour criminal charges of violating national security regulations and entering restricted military property against at least 400 immigrants.

They're accused of illegally entering the US as well as a 60-foot strip of land recently designated as a national defence area.

The military trespassing charges have been dismissed in at least 120 cases by magistrate judges at a federal court in Las Cruces, including rulings on Friday. Companion misdemeanour charges of illegal entry into the US were not dismissed.

The US attorney for New Mexico says at least 199 signs have been staked in the ground near the New Mexico border that warn against entry into the newly militarized area. But Chief Magistrate Judge Gregory Wormuth says, “The mere fact that some signs' were posted in the New Mexico National Defense Area provides no basis on which to conclude that the defendant could have seen, let alone did see, the signs."

The government was using a “cut-and-paste approach” in its allegations that allowed the court to use the same legal analysis in ruling in all the cases, Wormuth said in a court order.

The newly designated national defense areas are overseen by US Army commands out of Fort Bliss in the El Paso area in Texas and Fort Huachuca in Arizona.

The novel national security charges against immigrants who enter through those militarized zones carry a potential sentence of 18 months in prison on top of a possible six month sentence for illegal entry. The full implications are unclear for migrants who pursue legal status through separate proceedings in federal immigration court.

President Donald Trump's administration says it has authorised US troops to temporarily detain immigrants in the country illegally along the border — though there's no record of troops exercising that authority as US Customs and Border Protection conducts arrests.

Public defenders say the trespassing charges cannot stand without proof that immigrants knew of the military restrictions and acted “in defiance of that regulation for some nefarious or bad purpose.”