When the NHL's 2015 free-agent market begins on July 1, restricted free agents become eligible to sign offer sheets from rival clubs, provided they aren't headed to salary arbitration. This practice is rarely employed by NHL general managers. Still, a GM could attempt to sign away a top restricted free agent from a rival club.
As per the NHL collective bargaining agreement, a restricted free agent who didn't sign a qualifying offer from his team can sign an offer sheet with any club. His team then has seven days from the date the offer was accepted to match it.