Mainsail, RCW 9A.52.10, subsection 3, see bolded portion:
(3) "Enters or remains unlawfully". A person "enters or remains unlawfully" in or upon premises when he is not then licensed, invited, or otherwise privileged to so enter or remain.
A license or privilege to enter or remain in a building which is only partly open to the public is not a license or privilege to enter or remain in that part of a building which is not open to the public. A person who enters or remains upon unimproved and apparently unused land, which is neither fenced nor otherwise enclosed in a manner designed to exclude intruders, does so with license and privilege unless notice against trespass is personally communicated to him by the owner of the land or some other authorized person, or unless notice is given by posting in a conspicuous manner. Land that is used for commercial aquaculture or for growing an agricultural crop or crops, other than timber, is not unimproved and apparently unused land if a crop or any other sign of cultivation is clearly visible or if notice is given by posting in a conspicuous manner. Similarly, a field fenced in any manner is not unimproved and apparently unused land. A license or privilege to enter or remain on improved and apparently used land that is open to the public at particular times, which is neither fenced nor otherwise enclosed in a manner to exclude intruders, is not a license or privilege to enter or remain on the land at other times if notice of prohibited times of entry is posted in a conspicuous manner;
If there are signs conspicuously posted and you enter in violation of those signs, you are guilty of criminal trespass.
The list of defenses for Criminal Trespass are listed as follows:
RCW 9A.52.090
Criminal trespass — Defenses.
In any prosecution under RCW 9A.52.070 and 9A.52.080, it is a defense that:
(1) A building involved in an offense under RCW 9A.52.070 was abandoned; or
(2) The premises were at the time open to members of the public and the actor complied with all lawful conditions imposed on access to or remaining in the premises; or
(3) The actor reasonably believed that the owner of the premises, or other person empowered to license access thereto, would have licensed him to enter or remain; or
(4) The actor was attempting to serve legal process which includes any document required or allowed to be served upon persons or property, by any statute, rule, ordinance, regulation, or court order, excluding delivery by the mails of the United States. This defense applies only if the actor did not enter into a private residence or other building not open to the public and the entry onto the premises was reasonable and necessary for service of the legal process.
The first defense establishes that criminal trespass in the first degree does not apply to abandoned structures, though it is not a defense against criminal trespass in the second degree.
The third defense obviously is irrelevant if you ignore posted signs as the signs would negate the reasonable belief that the owner of the premises would allow you to be there in violation of the signs.
The fourth defense applies only to people serving legal papers and thus does not apply here either.
That leaves the only defense remaining:
(2) The premises were at the time open to members of the public and the actor complied with all lawful conditions imposed on access to or remaining in the premises
Note that this first requires that the premises be open to the public.
Posted signs would indicate that being unarmed is a condition of access to the premises. By willfully entering the premises in violation of this condition a person will have committed trespass. One may be willing to press the issue and hope that one is simply asked to leave, however the letter of the law is such that one would be open to prosecution.
That said, the charge would likely be Criminal Trespass in the Second Degree, which is a misdemeanor and not a felony and is not among the listed misdemeanors that would make one ineligible to hold a CPL. Even Criminal Trespass in the First Degree is still "only" a gross misdemeanor and should not affect one's CPL even if convicted.
I am not a lawyer, however. This does not constitute legal advice.
) in a govt owned "stadium"
