If they don't, there's a good chance that Softbank sues them into oblivion.
I am a little bit more cynical. The way the joint venture is construed gives a lot of power to the Chinese partners, after all they own 51% of the enterprize.
ARM will always have the CEO to blame if it continues to do business with China and the sanctioned companies.
It seems to me that is a brilliant way out to continue to sell to Huawei etc... which are under sanctions.
I imagine a dialog between ARM and US government:
-How come you continue to do business with sanctioned Chinese companies?
-I am sorry, We can't do anything. That is a majority owned Chinese corporation. There is nothing we can do except continue to supply to them. Even worse, the CEO has gone rogue.
-Well! Then we will sanction you!
- OK! There is nothing we can do. But, do you realize that 96% of all cell phones in the world use our technology? Including Apple! Are you certain you want to put us out of business?