Steve Peers, Professor of EU and Human Rights Law at the University of Essex, suggests that renegotiation of the UK’s membership of the European Union (EU) could be possible without treaty change (click on the link below for his article).
« So some have suggested the ?Danish solution?: namely a decision of the EU Heads of State and Government, meeting within the European Council, which constitutes the EU?s response to the renegotiation request, probably in conjunction with amendments to EU secondary legislation.
Such Decisions have been adopted in the past, as regards Denmark and Ireland, in order to address the former Member State?s difficulties ratifying the Maastricht Treaty and the latter Member State?s difficulties ratifying the Treaty of Lisbon. In the latter case, the European Council (ie Member States? Presidents and Prime Ministers) also agreed the broader legal and political context of this decision: the decision was ?legally binding?, it did not constitute a Treaty amendment, and its content would be set out in a Protocol to be attached to the Treaties in future. Indeed, the latter protocol was subsequently signed and ratified as promised. The UK could be offered a similar commitment. »
http://eulawanalysis.blogspot.co.uk/2015/05/is-it-possible-to-reform-eu-without.html