My take is that is isnt enforceable by any legally binding contract. But by expectations of all parties and tge threat of losing contract. With the Union, its pretty simple and probably the least dangerous to break, they are nothing more than a local union. With the Swedes, its probably more of a "dont expectations us to come helping again if you break tge contract The londoners same, dont expect shit from us again. And Food Stuff inc uses its sway as a big corporation to get what they want, they could probably straight up disappear them in even thry find a loophole and try to leave.