Mr Cameron is a wag. He's obviouly working on his stage act either for a slot on "The Comedians" or the forthcoming referendum propaganda. This is the second time I've heard him warming up today (the first was when I heard him say that people settling here who failed to learn English would be thrown out).
Declaration number 17 attached to the Lisbon Treaty (page 262 of this document):
http://www.eudemocrats.org/eud/uploads/downloads/Consolidated_LISBON_TREATY_3.pd
says this:
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17. DECLARATION CONCERNING PRIMACY
( moved from Art. I-6in the rejected EU Constitution)
The Conference recalls that, in accordance with well settled case law of the EU Court of Justice, the Treaties and the law adopted by the Union on the basis of the Treaties have primacy over the law of Member States, under the conditions laid down by the said case law.
...there was no mention of primacy in the treaty. It is still the case today. The fact that the principle of primacy will not be included in the future treaty shall not in any way change the existence of the principle and the existing case-law of the Court of Justice.
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There's a lot more legal waffle which you can look up yourself if you're so inclined. Basically the above says that although not enshrined in Statute (the Treaty) case law from decisions handed down by the European Court of Justice dictates that EU law trumps UK law.
Mr Cameron’s proposal is rather like a Parish Council introducing a bye-law exempting its parishioners from paying income tax and then passing another bye-law stating that their bye-laws have supremacy over UK law. It doesn’t quite work like that.
If you don’t like a club’s rules and you cannot get them changed there is only one option and that's to leave.