This isn't the first thing the courts have ruled against. But enforcement and compliance has been the real bottleneck.
The big difference here is that there is no real bottleneck.
Tariffs are a tax. Importers fill out paperwork as part of the payment process to show 'Yup, here's the payment for the 10% tariffs we gotta pay'. And they pay this money because they will get into legal trouble if they don't do so, just like you'll get into legal trouble if you refuse to pay type of tax.
And that's the key word here 'legal trouble'. Apologies for briefly going into more serious P&R for a second here but this isn't like the courts going 'Hey, stop grabbing and deporting people who are here legally' and then the admin continuing to do that before the courts can stop it.
The courts
need to be on board with these tariffs in order for them to be effective because if the court has ruled 'Yeah nah putting these tariffs in place was illegal', then there is no legal trouble for anyone who refuses to pay them. Even if the admin goes 'DON'T CARE WHAT THE CORRUPT AND RIGGED COURT SAYS STILL PAY THE TARIFFS OR WE'LL GO AFTER YOU IF YOU DON'T' well uhh that would absolutely not hold up in court because the case was literally saying 'Yeah he can't set tariffs like this'
And if Trump tells the USITC and CBP to keep collecting these illegal tariffs, they will be held in contempt and arrested and imprisoned. And sure 'What if he pardons them?', well he can only pardon to the crime itself - if he pardons these people and they go right back to trying to collect these tariffs, they can be arrested again for committing a new crime. And do you really think these people would want to keep on doing this cycle of facing arrest, jail time, then being pardoned just because the President told them to ignore this court order and keep trying to collect these tariffs?
(To say nothing of how this ruling has given him an out by spelling out exactly how he can do broad tariffs: it states that under Section 122 of the Trade Act of 1974, the president has the authority to enact a maximum 15% tariffs for a maximum 150 days, unless extended by Congress, specifically to deal with 'large and serious balance-of-payments deficits'. Which seems like 'Oh so what's changing then?' well I mean for starters - now he can't just go 'I DECLARE 40% TARIFFS EFFECTIVE IN ONE MONTH!!!' (people tell him that will hug the economy over so much) 'I DECLARE A PAUSE ON THESE TARIFFS THEY WILL BE 20% TARIFFS FOR 90 DAYS WHILE WE WORK OUT SOME GREAT TRADE DEALS, TREMENDOUS TRADE DEALS. THE MOST BEAUTIFUL ONES, THEY'LL BENEFIT ALL OUR NATIONS THE BEAUTIFUL ONES (THE US OF AMERICA) AND THE SLIGHTLY LESS BEAUTIFUL ONES', it's adding bureaucratic procedures that have to be followed and makes it so it's no-t just his random whims deciding if tariffs get paused, increased, decreased, etc.