There is pretty much no way to enforce so-called "international law" other than through sanctions or direct military action. Germany is not going to arrest Netanyahu if he visited the country. What would be the consequence of that? Nothing of substance, maybe a sternly worded letter from the ICC, but there are no effective and practical means of forcing them to act.

In order to avoid the problem, Germany would probably not allow Netanyahu to visit the country in the first place.

If I remember correctly, a former president of the USA cancelled a visit to Switzerland because they were wanted for war crimes. Would Switzerland have arrested that former president of the USA? Hard to say: cancelling the visit was an easier solution for the people who made the decision.

In Britain, an Israeli general arrived by plane but never disembarked because of an outstanding warrant for war crimes. Would they really have arrested the Israeli general? Hard to say: not letting them disembark was an easier solution for the people who made the decision.

Obliged by who? The US can choose to wipe their ass with whatever they signed and arbitrarily say NO to a request they don't like. Who's gonna hold them accountable for breaking their signed agreement?

Wasn't there the same pitfall with the League of Nations?

I was just answering your question my friend. Given the states are not party to the ICC, they have very little to do with it. But to your point: what teeth does the ICC have? In theory the 120ish other countries that WOULD arrest someone with a warrant, south korea, ausieland, canada etc. In theory.

The U.S. has never signed the treaty creating the ICC anyway.

The US is not a signatory to the ICC. The US legal position is that the bilateral immunity agreements it has with many (mostly non-european) countries that are signatories to the ICC prevent those countries from being required to arrest US citizens accused of war crimes. I'm not aware of any legal theory in or agreements that lets the US directly block the arrest of non-us citizens in a foreign country so it would have to be the result of backroom pressure.