I can find no such claim in the news, the articles all say “Venezuelan oil tanker”
Here's an actual industry source which captures the whole story in the headline https://www.lloydslist.com/LL1155836/Weve-just-seized-a-tank...
I still don’t approve of it, but it does appear to be “legal”
It's really a good thing the US did this, one less dangerous stateless vessel at sea. Trump admin does lots of bad things, this is beyond reproach.