In a word: Lawfare.

Start with the 1977 USSR Constitution:

Article 29

The USSR's relations with other states are based on observance of the following principles: sovereign equality; mutual renunciation of the use or threat of force; inviolability of frontiers; territorial integrity of states; peaceful settlement of disputes; non-intervention in internal affairs; respect for human rights and fundamental freedoms; the equal rights of peoples and their right to decide their own destiny; co-operation among states; and fulfilment in good faith of obligations arising from the generally recognised principles and rules of international law, and from the international treaties signed by the USSR.
Tibor Varady, THE IMPACT OF THE EAST-WEST DIVIDE ON INTERNATIONAL LAW – PATTERNS OF DISCOURSE AND THE WAVES OF 1989 (2010), which points out that Soviet practice (e.g., his Hungary) was, on its face, inconsistent with what was written. The Soviet explanation was an exception for "armed intervention for the purpose of 'safeguarding socialist democracy', or for the purpose of 'establishing democracy'" (Varady, p.9 pdf).

Thus, one might fairly argue, as did Sir John Rodgers (Sevenoaks), 1977 Parliamentary Debate re: Helsinki Final Act (Belgrade Meeting), that the Soviets were consistent only in their planned inconsistency:

To the Soviets, peaceful co-existence is merely an extension of the class struggle to the international arena—a political, economic, ideological struggle, but certainly not a military one. To the Soviet leaders detente helps to diminish the risk of a third world war, as can be seen in Mr. Brezhnev's speech to the Soviet Communist gathering last year.

I should like to read a short extract from that speech. Mr. Brezhnev said that:

"communists take as their starting point the general laws of the development of revolution and of the building of socialism and communism…. In our time, when detente has 524 become a reality, both in the international workers movement and amongst its opponents, there often arises the question how it influences the class struggle. Some bourgeois politicians express astonishment and create a fuss about the solidarity of Soviet communists and the Soviet people with the struggle of other peoples for freedom and progress. This is either naiveté or, most probably, the deliberate befogging of peoples' brains. For it is as clear as can be that detente and peaceful coexistence relate to interstate relations. This means that disputes and conflicts between countries must not be solved by means of war, by the use of force or by the threat of force. Detente does not and cannot in the least degree rescind or change the laws of the class struggle…. Strict observance of the principle of non-intervention in the affairs of other states, respect for their independence and sovereignty—that is one of the prerequisites of detente. We do not conceal"— I emphasise this— "that we see in detente the path to the creation of more favourable conditions for peaceful socialist and communist construction."
That is exactly what the Soviets are doing at the moment. Having read those words one might well ask "When is intervention not intervention?" The only answer there can be is "when it is practised by the Soviets".
Of course, in approaching issues of intervention and aggression, one should refrain from too much sanctimony - and, at the least, think about this quote:

“The ethic of our work, as I understand it, is based on a single assumption. That is, we are never going to be aggressors. . . . Thus we do disagreeable things, but we are defensive. That, I think, is still fair. We do disagreeable things so that ordinary people here and elsewhere can sleep safely in their beds at night.

"Is that too romantic? Of course, we occasionally do very wicked things.” He grinned like a schoolboy. “And in weighing up the moralities, we go in for dishonest comparisons; after all, you can’t compare the ideals of one side with the methods of the other, can you now? . . .

“I mean, you’ve got to compare method with method, and ideal with ideal. I would say that since the war, our methods — ours and those of the opposition — have become much the same. I mean, you can’t be less ruthless than the opposition simply because your government’s policy is benevolent, can you now?” He laughed quietly to himself. “That would never do,” he said.
Simon Chesterman, THE SPY WHO CAME IN FROM THE COLD WAR: INTELLIGENCE AND INTERNATIONAL LAW (2006; from le Carre, of course). One might ask: Who was speaking ? An "Us" or a "Them" ?

As we know from the Chinese version of "Unrestricted Warfare" (which includes Lawfare) is that the First Rule is that there ain't no rules. The impact of intelligence activities on sovereignty has been on the table for a long time. Quincy Wright et al, Essays on espionage and International law (1962; 120 pp. pdf), esp. Quincy Wright's "Espionage and the Doctrine of Non-intervention in Internal Affairs" (starting at page 17 pdf).

As a summary, we have Christi Scott Bartman, Lawfare: Use of the Definition of Aggressive War by the Soviet and Russian Governments (2009)

Abstract

This dissertation seeks to contribute to the understanding of the definition of the terms aggression and aggressive war by tracing the political, legal and military use of the terms by the Soviet Union from that posed at the 1933 Convention for the Definition of Aggression to the definition posed by the Russian Federation to the International Criminal Court in 1999. One might ask why the Soviet Union so adamantly promoted a definition of aggression and aggressive war while, as many have noted, conducting military actions that appeared to violate the very definition they espoused in international treaties and conventions. This dissertation demonstrates that through the use of treaties the Soviet Union and Russian Federation practiced a program of lawfare long before the term became known. Lawfare, as used by the Soviet Union and Russian Federation, is the manipulation or exploitation of the international legal system to supplement military and political objectives. The Soviet Union and Russian Federation used these legal restrictions to supplement military strategy in an attempt, not to limit themselves, but to control other states legally, politically, and equally as important, publicly, through the use of propaganda.
When I peer deeply into his eyes, I see a nationalistic KGB lawyer.

Hope this helps.

Regards

Mike