SANTA ANA . (AP) — A man who made millions from a string of illegal marijuana dispensaries pleaded guilty Monday to federal drug trafficking and tax offenses. The U.S. attorney's office said John Melvin Walker of San Clemente was one of 14 people named in a federal indictment in October following an investigation by the Orange County Sheriff's Department, the Internal Revenue Service and other agencies. Walker, 56, entered a guilty plea to one count of conspiring to distribute over a ton of marijuana and to maintaining drug-involved premises.