There are peacetime rules and war time rules, war time rules are best summarised as “government does what it wants and justifies it after the fact”.
https://en.wikipedia.org/wiki/Falklands_War_order_of_battle:... under “Ships taken from trade”.
It’s not at all clear to me a government would have that power about a foreign flagged vessel, even if the shipping line owning it might be British.
There are peacetime rules and war time rules, war time rules are best summarised as “government does what it wants and justifies it after the fact”.
https://en.wikipedia.org/wiki/Falklands_War_order_of_battle:... under “Ships taken from trade”.