So using Adobe Firefly is fine, since they only trained on data they had the rights to?
You can assert you own or have the rights to those images, based on your license with Adobe.
> we are declining to distribute your game since it’s unclear if the underlying AI tech used to create the assets has sufficient rights to the training data
So it seems that asserting "assets X and Y were generated by tool Z that has rights to its training data" would be sufficient. Presumably AI tools will also start to formalize that declaration alongside their terms of service.
I guess in that sense it's not provable by the platform, but it is provable by the actual copyright owner if you're infringing one.
What I mean before is that no human can know whether you used Firefly or SD or MJ or some other custom model.