It's a law, so nobody has to agree to anything. If want to sell access to a model, you have to open the weights.
It's Dario's plan that depends on every lab in the world agreeing.
Step #2 of his essay is "democratic coordination" among frontier labs and step three is coordination with China. I'm suggesting a single law Congress could pass that every US model company would have to follow on the same day, whether they like it or not.
Frontier progress is compute bound. Compute is bought with investor money. Investors put up tens of billions because they expect to sell the proprietary model that is created.
You're welcome to think the effect would be smaller than I do. But "it requires everyone to agree" is backwards.