based on what Eileen quoted from Marcilio, which I also consult - one could also be more "natural" and use "severing of the relationship between/among the parties.

Lacking further context, we may only assume that this is (as the previous two terms are) part of a legal dispute in which one party apparently acted as representative of the other one, without (in the opinion of such other party) having the appropriate power to do so.

Usually a service, distribution or similar agreement contains a clause titled "independence of parties" and is usually worded like "nothing in this agreement shall be construed as creating a partnership, agency, joint-venture, representation between the parties."

Now, such INDEPENDENCE OF PARTIES has apparently not been respected or the power of representation has ceased to exist or was invalid from the outset. And the represented party requests that the representation be declared invalid and the INDEPENDENCE OF PARTIES be confirmed.