That's a good solution. If the Cardassians are using their own freighters we can tag them and have the Caitians intercept without even needing to board, if they use a 3rd party like the Syndicate then we're probably boarding on completely acceptable pretenses anyways, and confiscating any weapons we can and warning the Caitians about the rest.Under whose authority? We're not at war with the Daiwar, and we're not even technically at war with the Cardassians. The Cardassians could ship in torpedoes in big unarmed container ships labeled, "We're shipping torpedoes, suck it Federation!" and we couldn't do shit about it.
But I don't want to be just a nay-sayer, so here's how it could actually work. The Caitians are at war and can put up a blockade. We could use our ships to scan for ships entering the region, not do anything about it ourselves, but tell the Caitians. Then Caitian ships could enforce the blockade, firing if their demands our not met. That would fall under the "quiet aid to the Caitians" option that was suggested as one of our alternatives.
I'm a little baffled that people are suggesting the Fed won't go for this kind of action when it's literally a major part of the plot resolution of a major TNG storyline. The situation is a tad different because there all that was needed was proof of Romulan involvement, but if the Federation was willing to like, literally publicly humiliate the Romulans I think we'll be fine here.
It's not a blockade if you confiscate things you've declared illegal, it's law enforcement!
Don't assume I won't like the ramifications if I want to CRASH THIS FLEETDon't wish for that. You won't like the broader ramifications.
WITH NO SURVIVORS!