Open Carry or Concealed Carry of Firearms in Public buildings in California is governed by California Penal Code 171(b).
California Penal Code 171(b) states:
(a) Any person who brings or possesses within any state or
local public building or at any meeting required to be open to the
public pursuant to Chapter 9 (commencing with Section 54950) of Part
1 of Division 2 of Title 5 of, or Article 9 (commencing with Section
11120) of Chapter 1 of Part 1 of Division 3 of Title 2 of, the
Government Code, any of the following is guilty of a public offense
punishable by imprisonment in a county jail for not more than one
year, or in the state prison:
(1) Any firearm.
(2) Any deadly weapon described in Section 653k or 12020.
(3) Any knife with a blade length in excess of four inches, the
blade of which is fixed or is capable of being fixed in an unguarded
position by the use of one or two hands.
(4) Any unauthorized tear gas weapon.
(5) Any taser or stun gun, as defined in Section 244.5.
(6) Any instrument that expels a metallic projectile, such as a BB
or pellet, through the force of air pressure, CO2 pressure, or
spring action, or any spot marker gun or paint gun.
(b) Subdivision (a) shall not apply to, or affect, any of the
(1) A person who possesses weapons in, or transports weapons into,
a court of law to be used as evidence.
(2) (A) A duly appointed peace officer as defined in Chapter 4.5
(commencing with Section 830) of Title 3 of Part 2, a retired peace
officer with authorization to carry concealed weapons as described in
subdivision (a) of Section 12027, a full-time paid peace officer of
another state or the federal government who is carrying out official
duties while in California, or any person summoned by any of these
officers to assist in making arrests or preserving the peace while he
or she is actually engaged in assisting the officer.
(B) Notwithstanding subparagraph (A), subdivision (a) shall apply
to any person who brings or possesses any weapon specified therein
within any courtroom if he or she is a party to an action pending
before the court.
(3) A person holding a valid license to carry the firearm pursuant
to Article 3 (commencing with Section 12050) of Chapter 1 of Title 2
of Part 4.
(4) A person who has permission to possess that weapon granted in
writing by a duly authorized official who is in charge of the
security of the state or local government building.
(5) A person who lawfully resides in, lawfully owns, or is in
lawful possession of, that building with respect to those portions of
the building that are not owned or leased by the state or local
(6) A person licensed or registered in accordance with, and acting
within the course and scope of, Chapter 11.5 (commencing with
Section 7512) or Chapter 11.6 (commencing with Section 7590) of
Division 3 of the Business and Professions Code who has been hired by
the owner or manager of the building if the person has permission
pursuant to paragraph (5).
(7) (A) A person who, for the purpose of sale or trade, brings any
weapon that may otherwise be lawfully transferred, into a gun show
conducted pursuant to Sections 12071.1 and 12071.4.
(B) A person who, for purposes of an authorized public exhibition,
brings any weapon that may otherwise be lawfully possessed, into a
gun show conducted pursuant to Sections 12071.1 and 12071.4.
(c) As used in this section, "state or local public building"
means a building that meets all of the following criteria:
(1) It is a building or part of a building owned or leased by the
state or local government, if state or local public employees are
regularly present for the purposes of performing their official
duties. A state or local public building includes, but is not limited
to, a building that contains a courtroom.
(2) It is not a building or facility, or a part thereof, that is
referred to in Section 171c, 171d, 626.9, 626.95, or 626.10 of this
code, or in Section 18544 of the Elections Code.
(3) It is a building not regularly used, and not intended to be
used, by state or local employees as a place of residence.
PS.: Good luck gettin' that Permit!
P.S.2: There is NO such thing as Assault Weapons, they work just the same as any other Semi-Automatic. When the Media says 'Assault Weapon' they just mean any Weapon that looks Scary.