TAOS, N.M. (Reuters) - The FBI on Saturday said it had arrested Larry Hopkins, the leader of an armed group that is stopping undocumented migrants after they cross the U.S.-Mexico border into New Mexico.

The arrest came two days after the American Civil Liberties Union (ACLU) accused the group of illegally detaining migrants and New Mexico’s Democratic Governor Michelle Lujan Grisham ordered an investigation.

Hopkins, 69, also known as Johnny Horton, was arrested in Sunland Park, New Mexico, on a federal complaint charging him with being a felon in possession of firearms and ammunition, the Federal Bureau of Investigation said in a statement.

“We’re not worried about it, he’s going to be cleared,” said Jim Benvie, a spokesman for the United Constitutional Patriots (UCP), blaming his arrest on political pressure from Lujan Grisham.

Hopkins is the “national commander” of the UCP, which has had around half a dozen members camped out on a rotating basis near Sunland Park since late February.

PATRIOTS OR FASCISTS?

The UCP describes itself as a “patriot group” helping U.S. Border Patrol cope with record numbers of Central American families crossing the border to seek asylum.

FILE PHOTO: U.S. soldiers walk next to the border fence between Mexico and the United States, as migrants are seen walking behind the fence, after crossing illegally into the U.S. to turn themselves in, in El Paso, Texas, U.S., in this picture taken from Ciudad Juarez, Mexico, April 3, 2019. The writing on the wall reads, "Help us Jesus Christ." REUTERS/Jose Luis Gonzalez/File Photo

Dressed in camouflage and carrying rifles, UCP members have helped U.S. Border Patrol detain over 5,600 migrants in the last two months, Benvie said. Videos posted online by the group show members telling migrants to stop, sit down, and wait for agents to arrive. Critics accuse the UCP of impersonating law enforcement.

Crowdfunding sites PayPal and GoFundMe on Friday barred the group, citing policies not to promote hate or violence, after the ACLU called the UCP a “fascist militia.”

“Today’s arrest by the FBI indicates clearly that the rule of law should be in the hands of trained law enforcement officials, not armed vigilantes,” New Mexico Attorney General Hector Balderas said in a statement of Hopkins’s arrest.

Hopkins was previously arrested in Oregon in 2006 on suspicion of impersonating a police officer and being a felon in possession of a firearm, according to the Southern Poverty Law Center.

NO STANDOFFS

U.S. Customs and Border Protection (CBP) said in a statement it did not support citizens taking law enforcement into their own hands and instead encouraged the public to be its eyes and ears on the border.

Benvie said the UCP was doing just that and had the support of local Border Patrol and police.

Mostly military veterans, UCP members carry weapons for self defense and at no time pointed guns at migrants, as they have been accused of, Benvie said.

Despite having funding sources cut off, Benvie said the group’s online support had swelled since it came under attack this week. Its Facebook followers have more than doubled since Thursday.

Asked what the group would do if told to leave by state police, Benvie said they would probably go and, if they felt the order violated their constitutional rights, sue the state of New Mexico.

“There’s not going to be any standoffs, this isn’t the Bundy Ranch,” Benvie said, in reference to a 2014 armed confrontation in Nevada.