The clause you're referring to is article 2, the non-derogation clause. That's an additional clause that ensures that a country cannot lower its labour standards to attract trade and investment. We don't have to make that proof for something to go to the review panel.
The proof at the review panel is twofold: there has to be a sustained course of action, meaning that this is not a single case; and it has to be trade-related. There is that proof. So things related to government unions, for example, could not go to review panels. These are the only criteria.