He's trying to claim that companies colluded to stop advertising on X and that violates antitrust laws.

https://en.wikipedia.org/wiki/Group_boycott

But it's strange because this refusal to advertise on twitter doesn't really harm competition in anyway. Concerted refusal to deal is supposed to be like when 3 big bad companies want to hurt a smaller competitive company so they get together and boycott any suppliers that deal with this competitor or force them to get a worse deal.

The companies GARM (Global Alliance for Responsible Media) represents are big enough (90% of advertising $) but they aren't really competitors to twitter. If say facebook and tiktok got together and told GARM they wouldn't run any of their ads unless they stopped working with twitter that would be much more in the spirit of the law.

But Twitter might still have a tiny bit of a case if they can prove they met GARM's standards but were still excluded anyway. I doubt that's enough for any major payouts though unless the judge is crazy. And honestly I think it's still dumb because even if GARM settles it just tells advertisers "Okay you can advertise on twitter if you want they meet our standards"...but are advertisers really going to want to advertise on the site that just sued them?

Also I don't even think GARM prohibits members from advertising with companies it doesn't recommend and just offers suggestions, which makes this case even more insane if that's true. In that situation it's like the health inspector gives a restaurant a "D" and the restaurant sues customers for not eating there anymore.