The US has placed Magnitsky sanctions on officials responsible for China's crimes against humanity in Xinjiang.
You'll have to ask policy and political science experts for the real significance, but I'll offer a comment or two... https://www.reuters.com/article/us-usa-china-xinjiang-sanctions/us-slaps-sanctions-on-four-chinese-individuals-including-xinjiang-communist-party-head-idUSKBN24A2GA

...from my perspective as someone who for the last 2-3 years has been trying to inform people, influential and not, about the unprecedented attack on Uyghurs, Kazakhs, Kirghiz, and other predominantly Muslim minorities in Xinjiang.

1st: for the US this is a long-delayed response. Big names from both parties in Congress, much of State Department, and other executive branch officials were on board for a strong response a full two years ago.

but Trump and trade-focused admin officials held out. Now Congress passed near-unanimous bill demanding sanctions, Trump's China trade deal is in tatters. Trump and Mnuchin finally gave the go ahead.

The UK conservative party just enacted the first post-EU sanctions and left out China. The conservative party is showing divisions on this, with calls from within to address Xinjiang & Hong Kong. This will give cover to the UK and add some pressure to impose their own sanctions.

Some will point out the Chen Quanguo and other sanctioned officials are more likely to see this as a badge of honor than a punishment. But I'd bet that official statements from China will soon show that the leadership as whole is not pleased with the sanctions.

Keeping in mind that I am a historian, not an IR specialist, here is my opinion of the significance: https://twitter.com/RianThum/status/1273358534286159872

China and others will continue to point out the US's own very real human rights violations and other failings. But governments are not monoliths. Many of the people who pushed for these sanctions would also love to end the US's own crimes (others enthusiastically support them!)

Opinions will differ on how much the value of actions that raise the cost of genocide is connected to the moral standing of those that impose the costs.

Those who are actually suffering from China's policies in Xinjiang (at least the one's who hear about these sanctions) will, of course, overwhelmingly cheer this development.

Finally, this is less significant but: on what basis is the US punishing family members of these officials? Do they have evidence that the family members are complicit? Is this standard? It seems grossly unjust, even if most of them probably do support the policies in question.

And I forgot to mention: if the standard for getting on the sanctions list is level of responsibility for the atrocities in Xinjiang, Xi Jinping obviously should be on the list.