Under Virginia Common Law, but only in the case where a felony is commited in the presence of the citizen. you may detain the person until local law enforcement arrives.
建議您看一下這個資料
http://en.wikipedia.org/wiki/Citizen's_arrest
同時在您"見義勇為"之前,您需要考慮,對方有兇器,您有家人,是否應該上前拔刀相助,隻有您可以做決定,