Virtue
Black's Law Dictionary · Henry Campbell Black, M.A. · 1910
Black's Law Dictionary
The phrase "hy virtue" differs in meaning from "under color." For instance, the proper fees are received by virtue of the offico; extortion is under color of the office. Any rightful act in office is by virtue of the office. A wrongful act in office may be under color of the office.
Phil. Law, 380.