- The EU is a international treaty whose signatories are sovereign nations. They...

- The EU is a international treaty whose signatories are sovereign nations. They can't really have a constitution in the same role as a nation state.

- No, commission can't overrule the EP. The parliament can reject commission-proposed legislation, and it can fire the commission.

edit: see the parliament doing its thing against ACTA here: http://www.rt.com/news/acta-committee-final-vote-365/