This case literally involves the courts getting involved in what should appear in trust stores. DigiCert was ordered by the courts to not revoke certificates via a TRO.

If the browsers removed DigiCert, DigiCert could certainly sue based on the harm to their business. They could argue that the browser vendors were inconsistent with the application of their rules. They could argue that the browser vendors were unfairly competing by kicking them out.

Not saying they would win all these, but they would certainly fight it - the alternative would be the end of DigiCert, they aren't going to go down without a fight in whatever venue they can find.

Is that really the claim, though? If someone chooses to punish DigiCert for compliance with the TRO then DigiCert might have grounds to file for declarative relief from the court, as the court could very well decide to help protect DigiCert from external consequences of their demand.