A country implements the most stringent environmental regulations in a region.
For a general statement/common knowledge like this, I cited a peer-reviewed journal paper, which has a similar claim in their introduction. However, the problem is neither this claim is the main findings of the journal paper, nor the paper provides any secondary citation. So it is a general claim made by the authors.
Can I cite the paper? or must I cite all the related environmental standards of all the countries from the region? I really think it is unnecessary, however, there is no such review in this region and in this subject.