The closest thing I could think of is other instances blocking the troublesome one. Maybe if they add support for moving your account to another instance, then you could just move in protest.

The decentralised nature of it makes that much harder. But also much less likely to be required.

For example, could you imagine a scenario where emails "go dark"? It'd require individual email services to go dark.

Communities can unfederate themselves at the click of a button (by an admin, of course). Or they can blacklist "bad" instances. Or whitelist specific instances and connect to nobody else.