The US Space Treaty rejected using the high seas as a legal metaphor. Instead it went with Antarctica.

The high seas are easy to use commercially, but also very prone to conflict. Wars are fought over tiny straits, and understandably so.

The Antarctic treaty decided the antarctic was too useless to fight over, so the signers decided to make it difficult to use in exchange for making it difficult to fight over.

Obviously space is a more like the seas. But nobody wanted a war over outer space (just look at the reaction to the Star Wars programs in the 1980s).

Antarctica is just a legal dead zone. What happens if a scientist on a station murders another scientist? On an American station, it was unclear until the 1980s. What happens if a passenger on a cruse ship murders another passenger? The FBI has people on standby - you'll be arrested when you return to your home port. Probably sooner.

The legalities are space are difficult because we decided to make them so. This is changing, and fast. Which is good.