[microcolonel]

Particularly at that time, there were no international courts that I know of who would have anything to say about a secret pact between two belligerents in the second world war.

The contract was to be enforced by the militaries of these belligerents, and to be interpreted and settled privately.

[sambe]

The International Court of Arbitration already existed, and there were other such courts even earlier.

It may well be the case that this was never intended as a formal contract, but I am responding to the assertion that there was no way for it to be. I stand by the claim: the issue is authority/power, not the necessary legal means.