While it could of course be produced in Xinjiang without using "slave labor," the US government banned those tomatoes in 2021 because of that risk:
https://www.cbp.gov/newsroom/national-media-release/cbp-issu...
If Costco were circumventing the ban it'd be a pretty big deal. I couldn't google up any indications that they are, so on balance I'd say it's "possible" in the same way my winning the lottery is possible. Can't rule it out, but reasonable people should probably bet against it.
TIL: Xinjiang tomatoes are something like 15% of the global market!
> TIL: Xinjiang tomatoes are something like 15% of the global market!
China consumes 37% of the world’s tomatoes. 80% of China’s processed tomatoes are from xinjiang. Fresh tomatoes are generally grown locally, but that is true around the world.