GREECE (CNN) -- With no sign of a functioning government in Greece, concerns are growing that this country could soon be forced out of the single currency. Citigroup puts the chances of a Greek Euro zone exit, or Grexit as it has been dubbed, at 75 percent. However, finding a way out of the monetary union may be easier said than done.

If you believe economists, the chances have never been greater that Greece is heading for the Euro zone exit door and one legal analyst has said EU leaders are already considering the possibility, even if they haven't admitted it. Edwards Wildman Palmer partner Charles Proctor says, "I think for many years talking about the possibility of exiting the Euro zone was taboo, but I think the dam has burst, so many people are now talking about it, not a possibility that can be ignored anymore, so the politics and the economics are in diametrically opposed positions at the moment."

Nina Dos Santos asks, "But wouldn't it be slightly incompetent of EU leaders not to be considering legally how they would deal with a situation whereby Greece were to want to exit of its own volition?" Proctor says, "One assumes a certain amount of contingency work is been done, but it's been kept secret among the political backdrop that the Euro zone must hold together."

Proctor says, "I think it's fair to note that a few days ago, ECB board member was asked whether ECB had contingency plans and he simply replied, "Well even if we do, I wouldn't tell you about them, especially watching a press conference."

What's standing in their way is the EU treaty, more than 400 pages long and no easy euro escape routes. Take for example article 128, "The provision states that the European Central Bank has the exclusive right to issue euro bank notes within the Union."

Proctor says, "It's quite clear from Article 128 of the treaty that only the ECB and the national banks within the euro system can issue bank notes as legal tender, so if Greece independently goes off and issues new bank notes that are supposed to be legal tender in Greece, then that would be clearly be a breach of this provision of the treaty."
Dos Santos asks, "And so what I suppose this means is that Greece has irrevocably surrendered its right to have a currency?" Proctor says, "They don't have the ability to create their own monetary system, they've transferred that to European institutions."

The current UK Foreign Secretary William Hague once said the euro was like a burning building without an exit. There is one escape clause inside this document but the consequences for Greece make it look more like a trap door than an emergency exit.

This is article 50, it doesn't mention a way out of the Euro zone, but it does offer a dramatic alternative. Proctor says, "Article 50 says any member state can decide to withdraw from the union in accordance with its own constitutional requirements. Unfortunately that only contemplates withdrawal from the EU as a whole and doesn't allow separate withdrawal just from the single currency. They could then try to reapply as a European Union member without being a Euro zone participant, but in practice I think that's not workable. I don't think it would be practical to do that in the time that's available, against the backdrop of a financial crisis."

Changing a treaty like this could take time and that's something Greece doesn't have these days which is why, some say, treaty change through the back door might have to do the trick. Proctor says, "Any solution would have to take place effectively outside this document. Withdrawal from the Euro zone by Greece would be a breach of the treaty without any question...but these things happen."

And if it does, the whole thing is up in the air again.