Should Hathaway wish to appeal the ban, ultimate authority will fall to commissioner Gary Bettman rather than to an independent arbitrator because the winger's suspension is for fewer than six games, according to Sportsnet's Elliotte Friedman.
Hathaway, who turns 28 on Saturday, was assessed a match penalty for his role in a melee that erupted between the two clubs late in the second period Monday night.
Six players were penalized as a result of the scrum.
The Capitals signed Hathaway to a four-year contract on July 1. He spent his first four seasons in the Calgary Flames organization.