What incentivises individuals to obey the decisions of courts? In the end, again, it's force, as monopolized by the state. If you don't abide by the court's decision, the state will take measures against you: it will impose fines, garnish wages, take away various privileges, and ultimately imprison you. If there were no such unpleasant and inevitable consequences, many people would simply ignore a tort judgment against them.

Was this the original idea of the UN? (Which has since oft been criticized for "having no teeth")