Русско-англо-русский юридический словарь

By virtue of law means: because of, in view of , on account of, by reason of, or owing to a law. (USLegal)

The phrase "by operation of law" is a legal term that indicates that a right or liability has been created for a party, irrespective of the intent of that party, because it is dictated by existing legal principles. For example, if a person dies without a will, his or her heirs are determined by operation of law. (Wikipedia)