The only thing that would probably have a chance of working is a large global coalition willing to take action simultaneously to sanction China's economy to the tune of at least being equivalent to a trillion dollars annually (whatever form that would need to take, a combination of targeting their companies, exports, imports, access to natural resources, banks, high level politicians, et al.). It would require at a minimum the US/Canada + EU + Japan + South Korea + AU/NZ. That gets you the majority of the global economy.

The big problem: it involves the world's consumers willingly punching themselves in the face at the same time. It might even throw the global economy into a deep recession and as a consequence kill a lot more people than the gulags are likely to. There are a lot of fallout problems in dealing with China, not least because they've historically shown a willingness to distribute any necessary pain upon their people to achieve party goals. There'd also have to be an elaborate verification program put in place, so China wouldn't continue their agenda in a more subtle manner; I don't see that sort of invasive foreign observation ever being allowed.

They've made a very conscious choice to eliminate the Uighur culture, as they did with Tibet before it. They have an end goal in mind, it's hard to imagine stopping them without upping the risks very high. Frankly I'm skeptical there is any way to stop them, I think they'd just take the pain and make it an us vs them conflict to convince the domestic population to absorb it (insert slogans here to drive loyalty during the great fight against the imperialists).