Ah, I think you're right. After 2014, it is no longer required to have each member state contribute members. Having said that, they still sit in the Council and the EP.
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It's not just international law, it's EU law. International law is... flexible, it can be bent and ignored. EU law takes legal precedence. That's hardcoded and whatever the legal problems in the UK are, they become void if they contradict EU law.
See, the UK agreed to this when they helped create the EU. Before anyone comes up with oppression again.