"Several characters have been shown to engage in vigilantism in the Dick Tracy comic strip. The Crimestoppers Club is a type of vigilantism, though one of their guiding principles is not to endanger themselves (or contaminate evidence) by engaging criminals directly".
They no more operate as vigilantes than members of the National Neighborhood Watch Network, or Curtis Sliwa/Guardian Angels. Commander Benson wrote the following. I apply this to the Club: ______________________________________________________________________________________________________________________________
Not under the U.S. Constitution [do they operate as vigilantes]. Ordinarily, private citizens, even those who take it upon themselves to uphold the law, such as vigilantes, are not subject to the Constitutional constraints imposed on official members of law enforcement. This means that vigilantes, acting on their own initiative, do not violate the Constitutional provisions safeguarding citizens' rights. But that does not hold when it comes to private individuals who act as "agents of the government". This description attaches when a private individual acts under the direction, advice, or coërcion of a government agency. Such persons are held to the same Constitutional requirements as official members of law enforcement. (That's why, if it's a violation of your Constitutional rights for a policeman to search your suitcase, he cannot get around it by asking some willing passer-by to do it for him.)
The definition of "agent of the government" doesn't require that the person be "a duly deputised officer of the law". All that is required is that the individual work under the direction or advice of a government agency, even a municipal one, such as a local police department. ______________________________________________________________________________________________________________________________
https://tvtropes.org/pmwiki/pmwiki.php/Main/CopsNeedTheVigilante
In truth, it doesn't matter if you're getting a paycheck; if you're working on behalf of the state, you're a state agent. That is to say, a cop can't ask you to do what he's not allowed to do.
https://forums.superherohype.com/threads/frank-millers-holy-terror.339379/page-15
https://www.kennethballard.com/?p=7555
One very important principle of law in the United States boils down to simply that a government agent cannot request or command a private citizen to do that which the agent is not authorized to do under the law. When it comes to the Fourth Amendment and the protection against a warrant-less search, this means simply that law enforcement cannot request a private citizen collect evidence they cannot otherwise obtain without a warrant or probable cause.
https://www.llrmi.com/articles/legal_updates/2018_us_v_highbull/
https://www.lexipol.com/resources/blog/cyber-tips-are-subject-to-the-private-search-doctrine/
"Moon Maid was shown to engage in vigilante acts, using her superhuman abilities to stop crimes that she encountered, such as robberies. This was often done with a disregard for the safety of her fellow citizens, but her acts were generally greeted with approval by Tracy and the police".
If she intervened in situations she only came upon as a passerby, then she did not act as a vigilante, bar perhaps the use of excessive force. If official police officers provided guidance to her, then she did not act as a vigilante.