Not true. From Handgunlaw.us:
Do “No Gun Signs” Have the Force of Law?“NO”
“No Firearm” signs in Colorado have no force of law unless they are posted on property that is specifically mentioned in State Law as being off limits to those with a Permit/License to Carry. If you are in a place not specifically mentioned in the law that is posted and they ask you to leave, you must leave. If you refuse to leave then you are breaking the law and can be charged. Even if the property is not posted and you are asked to leave you must leave. Always be aware of the possibility that responding Police Officers who may have been called without your knowledge and may not know the laws on trespass etc. could arrest you even if you are within the law.
It is legal to carry concealed in a public business that has a "No Firearms" sign, but if you are asked to leave, you must leave or you are trespassing.
Yes, that's what I thought.
If you are in a place not specifically mentioned in the law that is posted and they ask you to leave, you must leave. If you refuse to leave then you are breaking the law and can be charged.
They could ask you to leave if you broke their chewing gum ban.
Under this Aurora scenario, I highly doubt that the theater owner would attempt to sue the concealed carry person who interdicted the murderer by preventing other loss of life and injury because he did not heed their wishes.