Board Thread:Lore Discussion/@comment-26213507-20150715194939/@comment-1600847-20150819014301

Techinically, yes, the Stormcloaks are traitors. Rikke says "most were Legionnaires, once", such as Galmar and Ulfric. Thus, when they joined the Legion they swore fealty to Titus Mede, and are now in open revolt against him. Right or wrong in their reasons, that is still technically treason.