> yes but the opinion that it was illegal was the received wisdom by everybody with any sort of legal expertise in the subject

That isn’t true and you should really question whatever news source told you that. Putting aside that it was 6-3 in the Supreme Court. It was a 7-4 decision in the en banc Federal Circuit, with two Obama appointees voting in favor of upholding the tariffs. The lower appellate court opinions amounted to 127 pages: https://www.cafc.uscourts.gov/opinions-orders/25-1812.OPINIO....

You don’t get cross-party splits like that on issues where “everybody with any sort of legal expertise in the subject” agrees. If anyone with legal expertise was telling you that this issue was simple, they’re probably not very good at their job.