The so-called "Ioannina compromise" is one of the most talked-about and perhaps least well-understood issues relating to the ongoing reform treaty negotiations.

The term was coined after an informal meeting of EU foreign ministers which took place in Ioannina, a Greek city north of Athens, in 1994.

Broadly speaking, the Ioannina compromise is a gentlemen's agreement, a time-out or emergency break designed to reassure individual member states who fear fellow EU members may cut deals which they strongly dislike.

Ioannina gives countries a pause to find a solution

In essence, if a country feels that its vital interests are threatened but cannot muster a blocking minority, the decision is delayed while attempts to find a satisfactory solution are made.

The Ioannina mechanism was first proposed when foreign ministers from the then 15-member union were called to discuss how voting rules should change if Norway joined the EU.

At the meeting, ministers agreed that if EU members wished to oppose a measure but could not muster enough support to block it, they could ask the bloc's council of member states to do "all within its power, within a reasonable space of time, to reach a satisfactory solution" that would be acceptable to a qualified majority.

Norway eventually decided not to join the union, and the "gentlemen's agreement" remained little more than a curious appendix to the EU decision-making process.

It was superseded by the Nice Treaty of 2000, which established new voting rules for the EU ahead of the entry in 2004 of 10 new member states.

Poland's fight over voting rights resurrects Ioannina

But one of those newcomers -- Poland -- fought hard to resurrect it this year during bitter negotiations over national voting rights in the Reform Treaty.

And in a bid to find a satisfactory compromise, the then German presidency of the EU in June included a reference to Ioannina in an annex of the treaty.

According to the draft agreed last June in Brussels, the EU council is forced to freeze decisions if: "(a) at least three quarters of the population, or (b) at least three quarters of the number of member states necessary to constitute a blocking minority ... indicate their opposition to the council adopting an act by a qualified majority."

The annex does not place any formal time limits, saying that member states should spend "a reasonable time" looking for an acceptable solution.

Kaczynskis want more time and legal framework

But Poland is campaigning for a "reinforced" Ioannina mechanism and argues that two years constitutes a "reasonable time." Moreover, Poland wants the council to make an official decision on Ioannina in Lisbon and make it legally binding in some form or other.

Because the council normally tries to reach decisions by consensus, the original Ioannina compromise has been rarely invoked.

Experts say there was only one unsuccessful attempt to use it during its limited lifespan: a case involving Portuguese sardines.