1
general::
Also in virtue of. On the grounds of, by reason of, as in By virtue of a large inheritance she could easily afford not to work. [Early 1300s]
American Heritage Idioms
2
general::
Phrase(s): by virtue of something
because of something; due to something. • She’s permitted to vote by virtue of her age. • They are members of the club by virtue of their great wealth.
McGrawhill's American Idioms And Phrasal Verbs