I can find no such claim in the news, the articles all say “Venezuelan oil tanker”

Poor quality articles.

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 stand corrected, thank you.

I still don’t approve of it, but it does appear to be “legal”

It's generally considered best practice to detain these vessels as they tend to present a danger to ... well, basically everyone.

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.