Currently, AI models are trained using GPUs. In the future though, Generative AI will probably require its own specialized ASICs to achieve the best performance. This happened with bitcoin mining a few years ago and is also the reason big tech companies are making their own CPUs now.
Since there are only a few companies on the planet capable of producing these chips in bulk, the government could easily place restrictions on the purchase of AI hardware. This would control who has access to the best AI.
Only the government and a few permitted parties have access to the best AI. Everyone else would use worse AI that, while still good enough for most people, could be detected by the government. The government could use their superior models to easily detect whether a post is AI-generated, for example, and provide that insight as a service to citizens.
Effectively, the government becomes the sole purveyor of truth, as opposed to that power being in the hands of whoever can afford the biggest computer.
If they can afford the biggest computer, they can afford the licensing and legislative capture required to deal with your proposed restriction.
You don’t seem to understand corporations already rule the world. The government is not an effective check on them. Legislation gets written to cater to them. Yours would be no different. Even if it was a good idea on paper, it wouldn’t survive the lobbyists.