The City of Glendale’s proposal to pay the prospective Phoenix Coyotes buyers as much as $300 million over the next 20 years to run the City-owned Arena could be challenged in court for violating the Arizona Constitution’s gift clause.

Joseph A. Kanefield, a Ballard Spahr partner and a former assistant state attorney general, said the arena deal will have to be shown as being grossly disproportionate to similar transactions and to what the city would pay if arena management were bid competitively.

“That is where it gets a little bit stickier,” Mr. Kanefield said, adding that challengers will have to prove the arena pact is unreasonably far from market realities.