The arbitrator’s decision is binding and final. However, teams have “Walk-Away Rights” when the player elects arbitration. Teams cannot exercise these rights more than once per year (they can exercise this right twice in a year where three or four arbitration awards have been assessed to their players, but this is a very rare occurrence). If the award issued is for one-year and $3.5 million or greater, the team can (within 48 hours) tell the player, NHLPA, and NHL in writing that it does not intend to go forward with the award. Once this is done, the player is considered an Unrestricted Free Agent (UFA). But, if the award is for two years and $3.5 million per year or greater and the team decides to walk-away, the player will enter into a one-year deal for the compensation set by the arbitrator, and the player will be considered a UFA after the season. It should be noted that the $3.5 million threshold will be increased at the same rate as the Average League Salary every season (
this year's threshold is $4,084,219).
Found this article from 2017