Board Thread:Lore Discussion/@comment-26213507-20150715194939/@comment-1600847-20150719101329

JustAStormcloak wrote: Let me make this simple and short for you:

The Imperials send you to your execution just because you crossed the border and generally I join the Stormcloaks. To be fair, the Imperials tried execute you because they thought you were a Stormcloak, not just for crossing the border.

I don't doubt had the positions been reversed, i.e you'd been captured in a Stormcloak ambush in the presence of Tullius and his guard, that the Stormcloaks would have executed you too. If I were Tullius/Ulfric, I wouldn't take the risk.