On the matter of non-intervention in internal affairs the Helsinki Final Statement of 1975 states:
“VI. Non-intervention in internal affairs
The participating States will refrain from any intervention, direct or indirect, individual or collective, in the internal or external affairs falling within the domestic jurisdiction of another participating State, regardless of their mutual relations.
They will accordingly refrain from any form of armed intervention or threat of such intervention against another participating State. They will likewise in all circumstances refrain from any other act of military, or of political, economic or other coercion designed to subordinate to their own interest the exercise by another participating State of the rights inherent in its sovereignty and thus to secure advantages of any kind. Accordingly, they will, inter alia, refrain from direct or indirect assistance to terrorist activities, or to subversive or other activities directed towards the violent overthrow of the regime of another participating State.”