Chris

Slightly pedantic but relevant in this case:

“Legally binding” is a misleading term when discussing a treaty between two sovereign states (or as in this case one sovereign state and a supranational organisation representing a number of sovereign states). A sovereign state cannot ultimately be bound by any law. That’s what sovereign means. It may honour or renege upon treaties. The calculation is national interest, whether it is more beneficial to honour the treaty or not. The things the sovereign gains directly from the treaty, along with global reputation on the one hand, are balanced against the disadvantages of the treaty on the other - along with the possibility of damaged reputation and/or other sanctions imposed by other sovereign states.

Ultimately none of this is really law in the sense you implied by comparing it with your taxes. In that case, the sovereign sets the law to which you are subject. If you fail to pay, no judge passing sentence will start from the position that you were just a sovereign entity who had the right to decide not to pay (despite the efforts of some Freeman-on-the-land nutters to try these tactics in court from time to time). In statecraft the response to a recalcitrant rival is persuasion, sanction or all-out war. In the courts it is simply sentence.