Cooke said he expects more sheriffs will sign on to the lawsuit, but other sheriffs said they oppose the effort.
The County Sheriffs of Colorado, which represents the state's sheriffs, will not take part in the lawsuit.
"The Board of Directors made a decision this was not something that the association should join in," said County Sheriffs' executive director Chris Olson.
San Miguel County Sheriff Bill Masters said he doesn't think the new laws will be effective, but he won't join in the legal action. "I'm not going to sue anybody for anything. I understand the frustration but I wouldn't do that."