I've exhausted multiple resources, including the C.R.S., my own legal education, a textbook by West (they widely regarded as the leader in legal textbooks), three local friends who're lawyers, and a local friend of mine who's a judge (conservative) and who sits on these cases all the time.
They all say the same thing: If a property owner erects a clearly visible "No Firearms" sign and the patron can read it, they've satisfied the requirement of the law that the property owner's intent be clearly communicated. <--- That's the common law part of the trespassing law. At that point, entry with a firearm constitutes "unlawful entry" as per CRS 18-4-504(1). <---That's the statute part of the trespassing law.
In fact, there's a state bill currently in the hopper,
HB 12-1088, which expressly gives business owners the right to use deadly force against anyone who commits "unlawful entry" and the owner has a reasonable belief that the individual has committed, is committing, or intends to commit a crime and the owner believes the individual may use physical force, "no matter how slight," against anyone in the store.
I know, right? A House Bill (1094) that would have allowed businesses the same leeway as residences in using any level of force to repel crime and unlawful entry without prosecution or civil liabilities, was defeated in March of 2010. Therefore, the prior rule of justifiable force remains in effect for businesses. They're trying to resurrect that bill through HB 12-1088, and it would give business owners the legal right to blow us open-carriers away on any "reasonable suspicion" of committing a crime.
According to a pro-2A acquaintance of mine in the State Legislature who alerted me to this bill, the main reason they're pushing it is because store owners have seen a resurgence in open carry. He reports most of them are ok with it, but the few who aren't either don't know enough to post a sign, or have posted a sign. Some of those who've posted report OCers looking straight at the sign before walking in anyway. Those are the store-owners who are the most vociferous proponents of HB 12-1088. They have written their representatives, and those representatives are responding, first with HB 1094, defeated in 2010, and now HB 12-1088.
Is it really any wonder this is happening? When OCers refuse to respect the rights of property owners by ignoring posted signs while OCing, they will refuse to respect our right to keep and bear arms. The "in your face!" attitude not only won't work, it'll backfire, big time. If we're stupid and disrespectful, we'll get stupid handed to us on the pointy end of a stick. On the other hand, if we're smart and respectful, we'll succeed.
Respect the signs, and we may yet defeat HB 12-1088. Ignore the signs and you'll be adding fuel to the arguments of its proponents. As you all know, it takes the mere stroke of a pen to render a Constitutional right locally illegal, but it takes years to return that right to it's originally-mandated Constitutional status.
More on your link, Beau, in about an hour. Dinner awaits...
Actually, I'll tackle this one before dinner, as it's a piece of cake.
In reference to 18-1-104(3)'s "...unless it is described as an offense in this code...": Unlawful entry is a trespassing offense in this code. Unlawful entry is not a "common-law" crime. It's a statutory crime. What's common law isn't the crime itself, but the definition of "unlawful entry." It doesn't matter whether you refuse to leave after a property owner tells you, or you enter the premise in violation of and after having been informed of entry restrictions.
BOTH constitute trespassing, which is why
BOTH are mentioned in 18-4-504(1): "A person commits the crime of third degree criminal trespass if such person
unlawfully enters or remains in or upon premises of another."
Unlawful entry is a trespass.
Unlawfully remaining in or upon premises is a trespass.
The thing which makes it unlawful is your violation of the stated intent of the property owner. That intent can be conveyed the same ways a contract can be conveyed: Written or spoken. It's spoken when the owner walks up and and asks you to leave. It's written when the owner posts a sign indicating the conditions of entry. Whether you refuse his intent to have you leave or enter in violation of his written conditions of entry, it's precisely the same thing: You are violating the owner's property rights. That's trespassing.
Now - on to dinner!