David Cameron was interviewed on the Today programme this morning, and repeatedly pressed by Evan Davis as to whether he would oppose the new €+-26 Treaty being permitted to use the institutions of the EU.  He did not say he would attempt to forbid that.  Of course, a few weeks ago Nick Clegg stated in terms that that would not be forbidden.

If David Cameron had signed the proposed EU Treaty on December 9th, then there would have had to be a referendum.  I believe this proposition to be so clear as to be virtually unarguable.  Indeed, if David Cameron had signed that Treaty and not himself proposed there being a referendum, he would probably have faced an almost immediately leadership challenge.

Now, suppose that, instead of signing the new Treaty, Cameron had looked at the relevant piece of paper and nodded, and the Treaty had then proceeded exactly as if he had signed.  Do we believe that Conservative eurosceptics would have said "The fact that he nodded instead of putting ink on paper is sufficient reason for there not to be a referendum."  Why?  Well, because the fact that he would have nodded rather that putting ink to paper would have made no practical difference to anything.  If his nodding resulted in everything practical being done by the members of the European Union precisely as if he had signed, then why would anyone believe that should mean there didn't need to be a referendum?

Now suppose that instead of either signing or nodding, he simply shrugged and said – well, I'm not signing, but I'm not going to make any attempt to prevent there from being an EU Treaty.  The new Treaty may use all the institutions of the European Union.  Signatories to the Treaty may use the European Commission to provide research to support this Treaty.  The European Court of Justice will enforce it.  Not one single provision of the Treaty that would have affected the UK if I had signed should now not affect the UK.  Not one single additional provision that would have been in the Treaty if I had signed will not be in the new Treaty.  Everything that occurs within the European Union will occur precisely as if I had signed.

If he shrugged like that instead of signing, how would matters be any different from his nodding instead of signing?  The new Treaty would progress precisely as if he had signed.  The only difference would be that a little bit of ink would remain in a pen rather than be on a piece of paper.  The only difference from the nodding case would be that his shoulders moved instead of his head.

Now, lastly, suppose that instead of his shrugging, he shook his head – but otherwise everything proceeded exactly the same way.  So, he shook his head and didn't sign, but otherwise everything proceeded precisely as if he had nodded and not signed, or shrugged and not signed, or indeed as if he had signed.  (i.e. the Treaty used the institutions of the European Union etc..)

Under those circumstances, do we think that Conservative eurosceptics should accept that there didn't need to be a referendum?  Why would they?  If there is no practical difference whatever between his nodding or shrugging or shaking his head, why should which of those bodily actions – these pure gestures - he performed make any difference to whether or not there should be a referendum?

To be clear: I've always opposed there being a referendum.  I said we should renegotiate without a referendum.  But surely, surely the Conservative Party is not so easily taken in – so desperate to believe – that it thinks a pure gesture, of not practical impact whatever, is sufficient to see off pressure for a referendum?

If Cameron wants to say that his not signing the Treaty means there doesn't need to be a referendum, then there must be practical content to his not signing.  It cannot simply be the difference between nodding and shrugging.  The only practical content to a Treaty he did not sign, versus one he signed, is whether it is an EU Treaty – i.e. whether the new Treaty gets to use the institutions of the EU.  If he says it can, then there is no practical content in his "veto" whatever.  None.  Nada.  Nothing.  In that case, alas, there must be a referendum.  If Eurosceptics allow Prime Ministers to buy them off with pure physical gestures – to make shrugging one's shoulders rather than nodding one's head be the difference between whether or not there must be a referendum - then we can't claim to have any principles at all.