General Discussion

..but many of us have been wondering when republicans or even the conservatives on the Court would start to defend even their own preogatives and interests.

Here we see a strident defense of legislative preogatives under the Constitution to halt or limit what they basically understand as one man controlling their money. But there was a broader assertion of Executive authority here which some of the justices (a majority) picked up on and are addressing in their concurrences.

Trump has used the same assertion of Executive power on immigration, firing of federal agency officials, domestic military deployments and military operations overseas.

I mean, it's not as if he's completely blocked from imposing other tariffs with other regulatory schemes, so, this ruling and the language the Justices used to deny Trump wasn't micromanaging trade policy, but rather establishing limits on Executive authority.

Roberts made it clear that they were't addressing trade policy so much as they were ruling on legislative prerogatives and congressional authority, so I'd expect more of that as decisions come out from behind the 'emergency' shadow-docket orders that have explicitly dodged the question of congressional power.