http://leg1.state.va.us/cgi-bin/legp504.exe?000+cod+18.2-268.2
by driving on virginia state roads, there is implied consent
" Any person, whether licensed by Virginia or not, who operates a motor vehicle upon a highway, as defined in § 46.2-100, in the Commonwealth shall be deemed thereby, as a condition of such operation, to have consented to have samples of his blood, breath, or both blood and breath taken for a chemical test to determine the alcohol, drug, or both alcohol and drug content of his blood, if he is arrested for violation of § 18.2-266, 18.2-266.1, or subsection B of § 18.2-272 or of a similar ordinance within three hours of the alleged offense. "