Based on this court case from 2019 (pdf attached) determining that Trump can't block people on Twitter, they affirmed that his tweets are "government speech."
>Accordingly, while the President’s tweets can accurately be described as government speech
Based on that, I'm wondering if Twitter's actions are a violation of the Presidential Records Act (PRA) of 1978
>https://en.m.wikipedia.org/wiki/Presidential_Records_Act