Not in the 1789 law, which is why SCOTUS has struggled to define it in recent years. (This is not the first Alien Tort Act claim to reach SCOTUS in the last few years.)
Congress in 1789 was probably thinking about piracy-- if a Spanish pirate robbed a French ship, and took the loot to the U.S., the French shipowner could sue the pirate here.
In recent years, there have been attempts to bring suits under the Act over torture, genocide, terrorism and other things said to violate contemporary understandings of international law. The Court today basically kicked the issue back to Congress and told them to define the law better.
I think you’re right. Some of these legal terms from the 18th century — like “high seas,” for example — refer to places that are subject to international treaties because they don’t fall under the jurisdiction of any country.