While there might no specific rule in the book about untying your opponent’s skates, it’d make sense that it would be a penalty. Referee Johan Gossas of the Allsvenskan Swedish Hockey League may have been the first to actually call it.

Oscar Milton of Almtuna IS in the Swedish Tier II league spent two minutes in the box for untying the skates of IKO Oskarshamn’s Filiph Engsund.  Engsund also went off for his reactionary slash after realizing what happened.  Both were officially booked for unsportsmanlike conduct. 

Here’s an even closer look:

(stick-tap to Sport Uppsala for the original clip, and to @HockeyWebcast for a clearer look)