Dunno. The court filings say because it "unreasonably restrains competition in violation of the antitrust laws".
Can't say I buy that. Moving a team from a monopoly position in Phoenix to compete with the Leafs hardly sounds anticompetitive. In fact, I have no idea how antitrust laws even come into play here, because it's all the same league. Do the Leafs have that much sway in the overall league?
Presumably the NHL has got to like the fact that a team in Hamilton probably wouldn't lose the $20 million the Coyotes lose. The only thing that I can think of is a continued effort to grow the game south of the border would be helped by the Coyotes staying put. Am I missing something?