Hmmm, maybe I'm getting my information from a biased source, but what I've been told is that the vessel was circling WITHIN the Safety Exclusion Zone around the platform and ignored requests to move outsize said Safety Zone.

Russian Federation Law gives Russia jurisdiction over the "Northern Route" seas OUTSIDE the normal national waters limit and into international waters from the viewpoint of pollution and environmental protection.

The Arctic Sunrise is a SINGLE engine vessel and was NOT sailing in company of a Guard Boat or Safety Vessel which could take it under tow if its engine failed, in order to pull it away from the platform.

Therefore, from the Russian point of view, the movements of the vessel posed an environmental threat falling within the jurisdiction of the Russian Federation which justified its boarding.