Tyler Lang, 25, and Kevin Johnson, 27, each pleaded not guilty Tuesday at the Dirksen U.S. Courthouse in Chicago. They were indicted this month on charges of conspiracy and interstate travel to damage and interfere with the operations of an animal enterprise.

Johnson’s attorney, Michael Deutsch, told U.S. District Judge Milton Shadur he plans to file a motion challenging the constitutionality of the Animal Enterprise Terrorism Act, the federal statute under which the charges fall.

Outside court, Deutsch told reporters that among the issues with the law – passed by Congress in 2006 – are that it is overbroad and potentially criminalizes free speech rights protected by the First Amendment. He also said the act unfairly brands activism as terrorism.

“Freeing animals – does that sound like terrorism?” said Deutsch, who recently defended one of three protesters charged with terrorism-related counts during the 2012 NATO summit in Chicago.

Both longtime animal activists, Lang and Johnson were accused in the indictment of driving through Iowa, Wisconsin and Illinois in August with plans to damage animal farms. On Aug. 14, they stopped at a mink farm in Morris that “was in the business of breeding, raising and selling mink to fur manufacturers,” released about 2,000 mink from their cages, and spray-painted “LIBERATION IS LOVE” in big red letters on the side of a barn.

Neighbors told the Tribune this month that many of the animals were killed by traffic on the farm road leading into town, while others were found splashing in yard sprinklers and running through gardens. Dozens of the animals did survive, however, and were rounded up into cages and brought back to the farm, neighbors said.

The family that runs the farm declined to comment.

The day after the mink farm incident, Lang and Johnson were arrested by sheriff’s police near a fox farm outside Roanoke, about an hour south of Morris, after a search of their car turned up ski masks, camouflage jackets, bolt and wire cutters, muriatic acid, and reading materials on fox and mink, according to charges filed in Woodford County last year.

Both men eventually pleaded guilty to the state charges. Lang was given 30 months of probation, while Johnson is currently serving a 30-month sentence in state prison in Danville, records show.

If convicted of the federal charges, they each face a maximum of 10 years in prison, prosecutors said.

Johnson, who will remain in prison until at least mid-October, appeared in court in blue prison garb and did not speak during the hearing. Lang, dressed in a black sweater was freed on bail today after he agreed to not participate in any illegal animal rights activism while the charges were pending.