One cannot arrest and detain a trespasser as a "citizen's arrest" in Virginia in most circumstances. In fact, if one does, he could be criminally charged with Abduction!
It is best to call the police to report a trespasser.
Take pictures then call the cops.
R. Jason de Groot, Esq. We do not have an attorney-client relationship. I am not your lawyer. The statements I make do not constitute legal advice. Any statements made by me are based upon the limited facts you have presented, and under the premise that you will consult with a local attorney. This is not an attempt to solicit business. This disclaimer is in addition to any disclaimers that this website has made. I am only licensed in Florida. If you wish to contact the above attorney, see his profile at this website.