Which Takes Precedence?

Which takes precedence: international law or domestic law?

The situation in Japan and Germany is a bit ambiguous.

When I studied international law at Leiden University, it was explicitly stated that international law takes precedence over the domestic law of individual nations.
I remember wondering, "Really? Isn't that just a programmatic provision?"

Since the International Court of Justice is located in The Hague—in continental Europe—it’s worth noting that countries like France and the Netherlands clearly assert the primacy of international law.

Germany would likely want to take that same stance, but both Germany and Japan were defeated in World War II. I suspect they might be hesitant to make such a claim out of consideration for the UK and the US (though that is just my own impression).

In the case of the UK, international law only applies once it has been incorporated into their own domestic legal system. The same applies to the US—though, given that the US has a written constitution, the Constitution itself holds the supreme position.

Perhaps the UK is a bit of a special case?