Although states have their own laws and specifics that apply to a citizen's arrest, in the United States private individuals have the authority to make an arrest, even without a warrant. These are called Citizen's Arrests, or CA. An example might be if you see someone stealing a purse, you may on your own initiative detain the person stealing the purse. But there are lots of particulars you should know before you try.. Above all know the laws of your state.