The use of devices like ankle bracelets, popular in the U.S. legal system, could have prevented several recent terror attacks, saved millions of surveillance dollars, and might even have stopped the Saturday attack in London, said John F. Banzhaf, a George Washington University Law School professor.

“Requiring people who are already on a watch list, or are otherwise under suspicion as potential terrorists, to wear an ankle monitoring device permits law enforcement authorities to do what they cannot possibly do now – keep large numbers of suspects under effective surveillance,” said the public interest law educator Sunday.