I am not a lawyer. But I think cases need to work their way up to SC. Before today's ruling a Federal Trade Court ruled the tariffs illegal [1]. And later, a Federal Appeals Court did the same [2]
The process takes time.
1. https://www.cnbc.com/2025/05/29/court-strikes-down-trump-rec...
2. https://www.cnbc.com/2025/08/29/trump-trade-tariffs-appeals-...