EDIT: Some more info on the Thalmor related to the MQ, so I'll put spoiler tags since this thread is supposed to be more about the Legion questline or Lore spoilers.
Can anyone who "know" or are "enlightened" enough prove/disprove if the Imperial Legion (the Legion in Skyrim, at the very least) is doing anything to resist the Thalmor? Can we kill them legally if we join the Legion? Or maybe prove that they have fully submitted themselves to Thalmor rule?
So far, these are the points that indicate Imperial submission or resistance: (Feel free to post anything I've missed so I can add on to the list)
Imperial Submission
1) Banning of Talos Worship (I know they did it out of necessity, but still
)2) Imperial Soldiers in Full Elven Armour in Skyrim (not all)
3) Imperial Legion and Thalmor rumoured to "like" each other (in terms of faction relations like in Morrowind)
4) Thalmor Embassy in Skyrim (Depends on how you see it. Diplomatic thing or giving up land to an enemy?)
5) Allegedly bought out the deceased High King of Skyrim to allow Thalmor to patrol and hunt down Talos worshippers.
Imperial Resistance
1) General Tullius apparently dislikes the Thalmor but can't do anything due to orders.

The Stormcloaks seem to have the greater motivation at the moment.