I like the way you're thinking.
I wonder what the legal ramifications would be for a federal officer using a CA statute as an excuse for ignore well-settled 4A law (Terry v Ohio, et al).
Too early to share anything yet... but I think I may have just had an idea...
Let's briefly remind ourselves what 12031(e) says:
Who can perform a 12031(e) check? A peace officer. Where are peace officers defined? In Part 2, Title 3, Chapter 4.5 of the penal code, which is entitled "Peace Officers."
(e) In order to determine whether or not a firearm is loaded for the purpose of enforcing this section, peace officers
are authorized to examine any firearm carried by anyone on his or her person or in a vehicle while in any public place or on any public street in an incorporated city or prohibited area of an unincorporated territory. Refusal to allow a peace officer
to inspect a firearm pursuant to this section constitutes probable cause for arrest for violation of this section.
If you go through who is a peace officer, you'll see that it is a HUUUUUUGE list. Surely a national park ranger or park police would be found in the list, right?
But...no! This section below says both "Federal criminal investigators and law enforcement officers are not California peace officers" and "National park rangers are not California peace officers."
Now, there are a lot of little, "except when acting under code X" which I haven't checked yet, but taking this on face value, it appears that the federal police and rangers cannot perform 12031(e) checks.
830.8. (a) Federal criminal investigators and law enforcement
officers are not California peace officers, but may exercise the
powers of arrest of a peace officer in any of the following
(1) Any circumstances specified in Section 836 or Section 5150 of
the Welfare and Institutions Code for violations of state or local
(2) When these investigators and law enforcement officers are
engaged in the enforcement of federal criminal laws and exercise the
arrest powers only incidental to the performance of these duties.
(3) When requested by a California law enforcement agency to be
involved in a joint task force or criminal investigation.
(4) When probable cause exists to believe that a public offense
that involves immediate danger to persons or property has just
occurred or is being committed.
In all of these instances, the provisions of Section 847 shall
apply. These investigators and law enforcement officers, prior to the
exercise of these arrest powers, shall have been certified by their
agency heads as having satisfied the training requirements of Section
832, or the equivalent thereof.
This subdivision does not apply to federal officers of the Bureau
of Land Management or the Forest Service of the Department of
Agriculture. These officers have no authority to enforce California
statutes without the written consent of the sheriff or the chief of
police in whose jurisdiction they are assigned.
(b) Duly authorized federal employees who comply with the training
requirements set forth in Section 832 are peace officers when they
are engaged in enforcing applicable state or local laws on property
owned or possessed by the United States government, or on any street,
sidewalk, or property adjacent thereto, and with the written consent
of the sheriff or the chief of police, respectively, in whose
jurisdiction the property is situated.
(c) National park rangers are not California peace officers but
may exercise the powers of arrest of a peace officer as specified in
Section 836 and the powers of a peace officer specified in Section
5150 of the Welfare and Institutions Code for violations of state or
local laws provided these rangers are exercising the arrest powers
incidental to the performance of their federal duties or providing or
attempting to provide law enforcement services in response to a
request initiated by California state park rangers to assist in
preserving the peace and protecting state parks and other property
for which California state park rangers are responsible. National
park rangers, prior to the exercise of these arrest powers, shall
have been certified by their agency heads as having satisfactorily
completed the training requirements of Section 832.3, or the
(d) Notwithstanding any other provision of law, during a state of
war emergency or a state of emergency, as defined in Section 8558 of
the Government Code, federal criminal investigators and law
enforcement officers who are assisting California law enforcement
officers in carrying out emergency operations are not deemed
California peace officers, but may exercise the powers of arrest of a
peace officer as specified in Section 836 and the powers of a peace
officer specified in Section 5150 of the Welfare and Institutions
Code for violations of state or local laws. In these instances, the
provisions of Section 847 and of Section 8655 of the Government Code
(e) (1) Any qualified person who is appointed as a Washoe tribal
law enforcement officer is not a California peace officer, but may
exercise the powers of a Washoe tribal peace officer when engaged in
the enforcement of Washoe tribal criminal laws against any person who
is an Indian, as defined in subsection (a) of Section 450b of Title
25 of the United States Code, on Washoe tribal land. The respective
prosecuting authorities, in consultation with law enforcement
agencies, may agree on who shall have initial responsibility for
prosecution of specified infractions. This subdivision is not meant
to confer cross-deputized status as California peace officers, nor to
confer California peace officer status upon Washoe tribal law
enforcement officers when enforcing state or local laws in the State
of California. Nothing in this section shall be construed to impose
liability upon or to require indemnification by the County of Alpine
or the State of California for any act performed by an officer of the
Washoe Tribe. Washoe tribal law enforcement officers shall have the
right to travel to and from Washoe tribal lands within California in
order to carry out tribal duties.
(2) Washoe tribal law enforcement officers are exempted from the
provisions of subdivision (a) of Section 12025 and subdivision (a) of
Section 12031 while performing their official duties on their tribal
lands or while proceeding by a direct route to or from the tribal
lands. Tribal law enforcement vehicles are deemed to be emergency
vehicles within the meaning of Section 30 of the Vehicle Code while
performing official police services.
(3) As used in this subdivision, the term "Washoe tribal lands"
includes the following:
(A) All lands located in the County of Alpine within the limits of
the reservation created for the Washoe Tribe of Nevada and
California, notwithstanding the issuance of any patent and including
rights-of-way running through the reservation and all tribal trust
(B) All Indian allotments, the Indian titles to which have not
been extinguished, including rights-of-way running through the same.
(4) As used in this subdivision, the term "Washoe tribal law"
refers to the laws codified in the Law and Order Code of the Washoe
Tribe of Nevada and California, as adopted by the Tribal Council of
the Washoe Tribe of Nevada and California.
ETA: After looking through the various exceptions, it looks as though my first impressions were correct and the federal agents will NOT be considered peace officers, and therefore will not be able to perform a 12031(e) check. Now if they have written permission from the sheriff or police chief, then we can begin to discuss the wording of somebody who is "engaged in enforcing applicable state or local laws". But until then, we're clear.