The term "leftover" may suggest an afterthought, but the work left undone by EU leaders when they fashioned the Amsterdam Treaty is far from that. The unresolved issues go to the heart of the balance of power and of the nature of the Union as a forum in which sovereignty is pooled.
The imperative is enlargement and ensuring decision-making is not gridlocked by vetoes. That requires member-states to extend qualified majority voting to sensitive areas where in the past they have jealously guarded their right to say No.
For example, in the case of Ireland and Britain, any attempts by their partners to suggest that EU fiscal policy, notably taxation of companies, should be harmonised have crashed against the wall of unanimity. The Irish position is still evolving on other issues. Discussions are continuing within Government departments, with some officials arguing that Ireland's veto should be retained in aspects of social policy, which they see as an essential factor in our economic success.
Some 30 clauses where the veto applies are up for consideration, and each state has its own wish-list. The French, Belgians, and Luxembourgers, for example, would go to the wall to defend unanimity on the location of EU institutions. And no one will want to concede unanimity for quasi-constitutional clauses such as treaty changes or accession.
Agreement on one-commissioner-per-member-state, an Irish priority, seems reasonably secure, although the French and the Commission are still fighting a rearguard action for a smaller Commission with rotation of national representation.
They are likely to insist on a formula leaving the door open for a return to the issue, or to press what is, from an Irish perspective, only slightly more palatable, the idea of a two-tier Commission.
The other key leftover is the rebalancing of the weighted voting system within the Council of Ministers which has become more skewed in favour of the smaller states. The large states have insisted the quid pro quo for losing their second commissioner will be a more equitable reflection of their population weight.
But the issue is not simply large state versus small state - the relativities between large states are just as contentious. France (population: 57 million; votes: 10), for example, is insisting on maintaining parity with Germany (population: 81.6 million; votes: 10).
The Germans are understood to be willing to accept such parity as long as their overall relative weight is increased. But any formula to do so is likely to prove anomalous, opening up large gaps with countries such as Spain (population: 39 million; votes: 8) and eventually Poland, which has a similar population. Ireland (population: 3.5 million; votes: 3) favours an alternative which would leave intact the current method of calculating votes but would incorporate a requirement that any weighted majority should also reflect a population majority. Some variation on this is likely to be more easily negotiable than adjusting the present system.