Ley played junior with the Niagara Falls Flyers where he was one of the league's top point men. He was chosen 16th overall by the Toronto Maple Leafs at the 1966 Amateur Draft and returned to junior. After scoring 64 points in 53 games for the Flyers in 1967-68, the talented youngster was named to the league's first all-star team.

The scrappy rookie played well for Toronto in 1968-69 and was a regular through the 1971-72 season. He rushed the puck well and played an abrasive style in his own end. In 1972 he was one of the first players lost by Toronto to the rival WHA.

Ley spent seven years in the league with the New England Whalers and was a member of the first WHA championship team in 1973. He was picked to take part in the 1974 Summit Series versus the USSR and was named to the WHA first and second all-star teams once each. After scoring 27 points and playing well at both ends of the ice, Ley won the Dennis A. Murphy trophy as the top defenceman in the WHA. He returned to the NHL with the Hartford Whalers after the leagues merged and played a regular shift in 65 games while serving as the club's captain. He retired after laying 16 games the next season.

After his playing days ended, Ley took an interest in coaching. Ley guided the IHL's Muskegeon Mohawks/Lumberjacks for five years in 1980s and won the Turner Cup in 1986. In 1988-89, he was hired to coach the Vancouver Canucks' top affiliate, the Milwaukee Admirals. Prior to the 1989-90 season, Ley was named head coach of the Hartford Whalers. His tenure lasted two years before he was replaced but he landed on his feet as the Vancouver Canucks' assistant coach in 1991. Ley served as the club's head coach starting with the lockout-shortened 1995 schedule. He was replaced the next year by Pat Quinn but continued to work in the organization as a scout until he was hired as an assistant by the Toronto Maple Leafs in 1998.