If you are looking for case law and detailed rules/analysis, I would suggest that FlyerTalk isn't the appropriate forum -- beyond perhaps recommending a legal firm or entity (like AirHelp) to assist you in your claims.
Hm, well, I respectfully disagree. It should not be necessary to hire lawyers. It should be possible to end up concluding "Article x(y)z interpreted per case C-nnnn/yy means that in this case you can claim X from Y" in this or that situation.
I still think that the airline forums are the best place to find answers to that question. If I fly on RDU - CDG - VIE on a DL ticket but AF metal, the first place I'm looking for an answer to EU261 questions is on the DL forum
It's interesting you'd go to the DL forum, because my understanding is that the claim is against the operating carrier, not the marketing carrier.