Here is a perfect example as to what I mean when I say check the laws for the area in question and dont just take the advice of someone here on the board.ReefHound:If you're talking about citizen's arrest be very careful. In most cases it is limited to felony in progress and most importantly, the citizen does not have immunities and other protections that certified peace officers have. Better be extremely sure you have the right person and are doing the right thing, especially if the subject is not cooperative and it escalates into physical confrontation.
I find it hard to believe an officer is compelled to act, all he needs is doubt about the circumstances. Happens a lot in domestic cases where two sides dispute who has ownership or rights to property. Unless one side has compelling evidence, officers will likely just separate the parties to prevent physical violence and leave the rest to the courts.
Up here a citizen can arrest for any Misdemeanor they witness or has Probable Cause in a Felony. The Felony would most likely be done by a LEO and by-pass the citizen just using them as a witness.
99% of the time the citizen calls the LEOs to do the actual contact but they are the ones that tell the bad guy they are under arrest or that they are issuing a citation. In this neck of the woods the citizen will be advised by a LEO if it is advisable to arrest/cite or not. They have better protection against false arrest than the LEOs have but are still subject to a civil suit.
Domestics are a totally different story. If there is a property dispute it will go to the courts for sure as we are a community property state. Whats his is hers and whats hers is his period. If a domestic is the least bit physical the aggressor goes to jail. The prosecutor doesnt like it when both halves get booked in but it happens once in a while.
How do you separate the parties in a domestic if one doesnt agree to stay elsewhere? After all if they are living together or still married each one has the same rights to the property.
Different laws and actions for different areas.

Gary D.