I mean, he can’t. Even if he claims to have the executive power, even if he found a bunch of lackeys willing to try to do it for him, he can’t do it. Whatever he did would be unenforceable. You can’t just turn off the Internet. That’s literally the reason we invented it in the first place, it’s a communication network resilient against nuclear strikes and war and bad-faith governance all at once.

He could probably make it very hard to use, given a lot of time, but he’d be eaten alive by the angry populace long before it ever reached that point.