Only works if you find someone to pay. I listened to a lengthy (German) podcast about international maritime law. To sum it up: you can’t do that much, because you won’t find the responsible person/company/state.
> (German) podcast about international maritime law
Russia isn’t even pretending to follow international maritime law. China hasn’t for a decade. And now America is being creative with its interpretations.
Most of the water isn't internal.. getting in and out of the baltic sea goes past Sweden/Denmark.
But we probably have promised not to blockade ships in some conventions. And little Denmark (or Sweden) do not benefit from setting a precedence that conventions can be broken.
Getting payback is easy though: support Ukraine.
Or at least a responsible person with money to pay for it. There are plenty of cases of some poor sailor getting stuck with the bill and forced to live on the abandoned boat as a result.
You can always make the regulations such that they're actually effective. You could require the company providing the bond be from a reputable country, for example.
Still I don't see an issue - basically you either pay the armed coast gard cutter that stands in your way or you don't go through the straight. If you don't cause any trouble, the other cutter on the other end will pay you back. No money, no transit - unless you really like being boarded.
The Outlaw Sea, https://us.macmillan.com/books/9780865477223/theoutlawsea/ , is a book about all of the ways international water is essentially lawless.
> German podcast
There was a Planet Money episode touching on Maritime law:
https://www.npr.org/2025/10/17/nx-s1-5577076/shadow-fleet-ru...
It was about Russian tankers breaking the sanctions, but with a well put explanation of why we can't just stop these ships even with extreme confidence in their fraudulency.