On April 24, 2023, the Supreme Court declined to hear an important case about greenhouse-gas litigation. This was a setback for WLF, which filed an amicus brief supporting the petition. Splitting from the Second Circuit, the Tenth Circuit held that claims about climate change arising from greenhouse-gas emissions are not exclusively governed by federal common law. The court also held that plaintiffs may artfully plead around federal jurisdiction by invoking state law. WLF’s brief explained why the Tenth Circuit’s decision will have devastating consequences and why federal common law governs Boulder County’s claims. The brief also explained why the Court should not allow parties to plead around federal jurisdiction.