If anything, Loper would make it easier for the Forest Service, since it was the reissue of the (long-expired) permit in 2018 that would fail court examination

If anything, Loper would make it easier for the Forest Service, since it was the reissue of the (long-expired) permit in 2018 that would fail court examination as "arbitrary and capricious." And that permit was only for 5 years, so the re-issued permit expired in 2023. No matter how the law is interpreted, BlueTriton does not currently have a valid permit to take water from this spring. The Forest Service order is just the second order barring them from using this water; the California water board has already issued a cease-and-desist, and Loper would have no affect on that order.