You should run a search for the department of game and wildlife, or the Colorado equivalent. They should have a section on the Administrative Code or similar statutes that you can look up. Here in Virginia, the list can be found here: http://leg1.state.va.us/cgi-bin/legp...g+4VAC15-30-40

I'm sure Colorado has a similar document. BTW, they may not be illegal to own in the state, but it would be against the Lacy Act to cross state lines with one. Believe it or not, that would be a federal felony.