It's all really a matter of splitting hairs anyway, and Robin Hood's actions were still of a "treasonous" nature. Heck, William Wallace was drawn, hanged, and quartered, in part, because of his "treason" against a king he never felt he owed any allegiance to in the first place!

One groups', nationality's, or country's freedom fighter is often another group's, nationality's, or country's traitor.