He studied drama at the University of Hawaii and appeared in several university stage productions. After graduation, Law moved to New York, where he studied with Elia Kazan's Lincoln Center Repertory Theatre and had a small role in Garson Kanin's comedy Come On Strong (1962).
He was best known for his roles as the blind angel Pygar in the science fiction cult classic Barbarella (1968) with Jane Fonda, and as news anchor Robin Stone in The Love Machine (1971). The latter reteamed him with Alexandra Hay, his co-star from the 1968 "acid comedy" Skidoo. He worked as a film extra as a child, and had a non-speaking role as a courtroom page in John Sturges's The Magnificent Yankee (1950).
Like many American actors he moved to Italy where he acted in several films. One of these was seen by the director Norman Jewison, who thought Law perfect for the role of a young Soviet sailor in The Russians Are Coming, The Russians Are Coming (1966). He followed this with a co-star role in Otto Preminger's Hurry Sundown (1967).
Law returned to Europe where he played the lead in a spaghetti western, Rides a Horse (1967), then the title role of Danger: Diabolik (1968), and played an angel in Barbarella. He followed this with The Sergeant (1968) with Rod Steiger. Tall and handsome, with steel-blue eyes, Law became a sex symbol in the 1960s.
He was a VIP guest at Hugh Hefner's Playboy Mansion and in Hollywood society. Law co-starred in Roger Corman's film Von Richthofen and Brown (1971), playing Manfred von Richthofen opposite Don Stroud's Roy Brown. Corman used Lynn Garrison's Irish aviation facility, complete with replica World War I aircraft.
Garrison taught Law the basics of flying so that he could take off and land, making some of the footage more realistic. Some other of Law's movies have also become cult classics, including The Love Machine (1971), The Golden Voyage of Sinbad, and Attack Force Z. Two of Law's films, Danger: Diabolik and Space Mutiny, were also featured in the movie-mocking TV series Mystery Science Theater 3000. In 2001 he appeared in Roman Coppola's directorial debut CQ, an homage to the Italian spy/sci-fi B-movies in which Law often starred during the 1960s.
Law's final credited film role was in 2008's Chinaman's Chance. On December 13, 2007, his doctors diagnosed him with pancreatic cancer. Law died five months later on May 13, 2008 at his home in Los Angeles.
His remains were cremated.
Fellow American Association for the Advancement of Science (chairman of the section 1996-1997, member-at-large section since 1997), California Academy Sciences (honorary). Member NAS, American Academy Arts and Sciences, American Chemical Society (award in pure chemistry 1973, Harrison Howe award, 1976, R.C. Fuson award, 1986, James Flack Norris award 1986, Arthur C. Cope scholar,1986, Executive Committee physical chemistry division, commission on science 1992-1997), British Chemical Society, Sigma Xi, Phi Lambda Upsilon.
Married Sharon Lea Kruse, August 22, 1964. 1 daughter, Kate Andrea.