Does that apply to secret squirrel Reserve Deputy Sheriffs, with the proper "credentials"?
No since they do not have powers of arrest and IIRC they'd have to be academy trained prior to having the power to arrest someone.
There is much question/confusion in the LE community right now on this part of the law.
I should be doubly qualified under this law, but like many lack proper "retired" credentials, plus most LEOs would claim that Constables aren't really "police" (they love to substitute that word for the term "law enforcement officer" that is in LEOSA) even though we have statutory arrest powers. I'd call it risky business right now until the goons at the State analyze it further and come out with some guidelines (which will likely not agree with the black letter of the law).