A vote for the UK to remain in the EU will have legal consequences as well as a vote to leave, a senior advocate has said in an address.

Kenneth Campbell QC outlined some of the legal issues that would arise in a presentation to an event organised by the Advocates Group on European Union Law (AGEUL).

Mr Campbell commented that a good deal had been spoken and written about possible legal issues if there were a “leave” vote, but much less about the potential consequences of Britain opting to stay in the EU.

“Indeed, I was chatting recently with one lawyer about giving this talk who said to me that it would be a pretty short event… [but] there is more to it than complete continuity.”

He went on to explain the legal consequences that would follow from the package negotiated by Prime Minister David Cameron with other EU leaders, that triggered the referendum campaign. 

While the decision containing the agreement anticipated future changes to the EU treaties, in his view it bound the member states as an agreement in international law and contained a number of legal obligations.

"Taking that a step further," he continued, "it seems to me that nonetheless it could potentially serve as an instrument for interpretation and clarification of member states’ obligations in connection with the treaties in those areas which are affected by the subject matter of the decision."

Discussing the procedure by which the decision might be given effect, and the effect of a commitment to make changes to the treaties, Mr Campbell said this would require the involvement of the European Parliament in amending the underlying legislation in the areas covered by the decision. These included co-ordination of social security systems, the "emergency brake" on free movement of workers, and the right of EU citizens to move and reside freely in other member states.

"You will immediately see that all of these provisions relate to areas of core EU policy, and areas moreover which are currently hugely politically contentious, particularly those around free movement. So it is quite conceivable there may be challenges in managing the legislative process, since whatever political compromises were involved in the Council are not, of themselves, binding on the European Parliament."

He also speculated that the measures might give rise to judicial challenges, especially by those affected by the restrictions on freedom of movement. "There are parallels in litigation which is currently taking place in the Upper Tribunal about social security entitlements of citizens of the most recent accession states."

Click here to view the full address.