Depends on what you mean, clients like apps on app stores and websites can be taken down sure, but you could run a client on your device, instead if you couldn't access a website or app

The relays storing the posts, if governments go after companies running relays they might be able to take the content down or asking them to blacklist certain relays, but the content will still be available somewhere on another relay to be accessed 

So you can always take your account and content to another client, if you were removed from a certain front end/client