Not sure what you're saying here. They were arguing before the Supreme Court ruling that they had the authority to impose tariffs under the
International Emergency Economic Powers Act of 1977, but the court ruled that act actually doesn't allow him to do that because the Constitution gives tax power to Congress and they can't give that away without explicitly doing so and the act doesn't mention tariffs at all. This seemed extremely clear and it's why a bunch of us in this thread have been predicting this decision since the court took the case.
He's justifying the new tariffs in the exact way he said he'd resort to back when the Supreme Court first took the case--
the Trade Act of 1974. That one didn't justify a bunch of his prior tariffs because it explicitly limits the amount to a 15% tariff for up to 150 days and most of his old tariffs were well above that 15% rate. I don't think it justifies these new ones for a different reason--there's no actual emergency, and the 1974 act requires one. Most of the tariffs he changed have been unchanged for decades and trade imbalances with those nations have also been there for decades. What's new? Almost nothing. If he hasn't already been sued over the new tariffs he soon will be, and I don't see why he won't lose that case, too. He might've been able to make a case by only tariffing certain countries like China where the trade imbalance changes every year, but doing it to EVERY country makes the case against the new tariffs being due to emergency easy to prove.
My main surprise in the decision is that Kavanaugh somehow sniffed his own ass enough to convince himself that IEEPA somehow gave the president the power of the purse which is definitely does not. His reasoning is full of logical fallacy that I can't make complete sense of without a dozen or more "but you're ignoring..." thoughts as you read through his logic. I had hoped Alito and Thomas would take the same originalist view they usually do with law but hey, they've always been politicians more than judges so I'm not surprised by them voting for their team.
I'm also surprised Trump threw a tantrum and just put a blanket 10% and then 15% tariff on everyone again. You can evaluate Trump's ideas on tariffs somewhat charitably by pointing out that he actually did work out a bunch of deals with dozens of countries to get more back from them than they previously ever gave us by threatening them with tariffs that would presumably last at least three years and more likely longer than that. Several countries had given concessions to get their tariff down below 10%...and now they get punished and reset back to 15% WHY, exactly? Because Trump is pissed at the Supreme Court taking his ball away and wants to flex in the mirror while ignoring the diplomatic price of doing that? Any country that negotiated with Trump in good faith just got kicked in the nards. Why would any of them renegotiate yet again with him when he's so inconsistent?