Obviously the FBI can seize your domain, which has happened plenty of times.

But also: https://news.ycombinator.com/item?id=17083333

You don’t own a domain, you rent it.

You only "own" something on a blockchain so long as someone cares about that blockchain. Your keys can also be stolen or lost so your "ownership" is as tenuous as the security of your keys.

Blockchain content isn't much more permanent than content hosted on a traditional server.

Is this a common problem that Web3 solves?

I understand it makes it more difficult, but they could seize your keys or your person and force you to turn over your keys.

Either way that seems like a legal issue, not a technology issue.