What the attorney is saying is true. The Colorado laws trump the federal laws if whatever product is being argued about has not crossed sate lines. Thats the 10th Amendment. The feds keep on wanting to use the commerce clause of the constitution to fight these cases but its not legally relevant. The commerce clause is only for products that cross state lines.
We've already seen a couple states that have used this argument to allow there state residents to own silencers, fully automatic weapons and so far the feds have done nothing about it. Its obvious that the feds don't want to take on a state government directly because that will lead a case to finally being forced to go before the supreme court to make a definitive decision about what exactly the 10th amendment allows. They know they'll lose.