Board Thread:Lore Discussion/@comment-26213507-20150715194939/@comment-1600847-20150831142613

Blademaster Jauffre wrote: It's not a civil war qeust, I just checked it. Game-mechanics wise no, it's not.

But it still involves the Civil War and affects it. Thus, you cannot complete the Main Quest without getting involved in the Civil War. Not the questline, but the event.