Not a lawyer, but I thought that one element of a binding contract (at least in the common law Anglosphere) is that the parties must intend to create a legally binding relationship - i.e. if two friends agree to each do a favour for each other, and one of them reneges on their promise, the courts won't hold that it's a contract because in general if you ask a friend to do a favour for you, it's not understood to be a formal legal relationship.

I wonder how that applies to embargoes that don't come with formal NDAs or whatever.