After France and Germany sent a letter to the EU opposing the accession of Romania and Bulgaria to the Schengen zone (a decision each Schengen member state has a veto on), Romania has hit back with suggestions that it will delay Croatian accession (or that the CVM [Co-operation and Verification Mechanism] that applies to it and Bulgaria should be applied to Croatia as well), and that it might delay ratifying the Protocol allowing the 18 Lisbon MEPs from taking their seats in the European Parliament. France and Germany are blocking the expansion of the Schengen zone to include Romania and Bulgaria because of their failure to make good progress in combating corruption and organised crime. However, technically both Bulgaria and Romania have met the criteria for acceding to the Schengen zone, and the two sets of criteria are supposed to be separate.
Romania's fight-back has been couched in the language of the rights of small states against the power of the Franco-German core. Ironically, a few days before EUobserver reported the Franco-German letter, I heard this policy being held up as an example of successful small state diplomacy - the Netherlands was extremely reluctant to let Romania and Bulgaria join, and wanted to put pressure on them to speed up justice reform. (Justice, immigration and law and order are policy areas the Dutch government is very keen on). Though the Netherlands has a veto in this area, using the "nuclear option" isn't a great diplomatic technique, and it's much better to get wider support for their position, so the Dutch lobbied the other states (particularly France) on the issue. (Yet another example of the veto not being a practical tool in European politics, I think).
In any case there's the question of whether or not it's right to move the goalposts like this. Wikileaks, as the EUobserver reported, has shown the considerable frustration in the EU over the the failure of the 2007 accession states to effectively fight corruption. The EU has been lax and hasty in its enlargement, and there's little incentive for states to reform after they've joined. It is hard to see how corruption and organised crime can be divorced from the burden Romania and Bulgaria would have to assume in becoming the EU/Schengen zone's border. Would border controls be or remain effective?
It may be unfair to tie these issues together after the fact, and the EU should have perhaps linked them more closely earlier, but these issues aren't optional for Romania, Bulgaria or the EU, and we have to find some way of ensuring that they will be tackled. There is a big question over big states versus small states rights, but this is not the most glorious way of fighting the small states' fight - because in the end this is about Romania and Bulgaria living up to the commitments of membership, which will benefit them and and EU.
UPDATE: Romania has given up on this strategy. Also worth reading is Kosmopolito's critque of Romania's brand of EU politics.