Giving power to national parliaments is a common theme of EU reform. Expanding the power of the European Parliament, it's argued, has failed as can be seen from declining turnout. I don't buy the turnout theory, largely for the reasons Jon Worth has argued over at the LSE blog: there hasn't been a link between the European elections and the policy direction of the EU, never mind the people who run it, making the influence of the EP and the importance of the elections rather nebulous - and hardly exciting for citizens. It wasn't until Juncker was elected Commission President by the EP on the basis of the Spitzenkandidaten and election campaigns that the elections showed their true value, and we have to wait until the next election to see if the Europarty primaries and the campaigns generally come under greater scrutiny for their policy platforms.
The low turnout argument has led to some arguing that the EP should be replaced by the original assembly of national parliamentarians, or that there should be an upper chamber of national parliamentarians. But this wouldn't increase the legitimacy of the EU. The idea that national MPs would return home to discuss European decisions that have no bearing on their re-election clearly has no traction. Frankly, the hope here is that national MPs will socialise themselves into being more pro-European and this will tone down the anti-EU rhetoric at home - but European decisions are too political now not to have a direct democratic input. This is no solution for boosting EU legitimacy.
What about giving the national parliaments a red card power to block EU legislation? This idea has more merit, but to me it's coming at the question from the wrong angle. A system where you can block a lot, but where it's hard to make any decisions that are effective or that people can be happy with loses legitimacy simply by not working very well. By contrast, simple and direct democratic controls would give citizens a more direct route to the EU - compare the old way of picking the Commission President. Technically, it's still there - there's an election, the European Council considers the outcome and nominates a candidate that the European Parliament votes on. How is any voter going to engage in the elections based on that? But now that the winning candidate (with a majority in the Parliament) will be elected, it's a lot simpler and potentially more engaging.
It's the same with a blocking vote for national parliaments - it could prevent unpopular legislation, but it could also block solution-finding and decision-making so much that voters can't see how they can influence any outcome that they actually want. Which is why there needs to be a democratic European forum for European decisions.
But that doesn't mean that the national parliaments shouldn't have a bigger role at a European level. By building on the Yellow Card process, real substance could be given to subsidiarity. What decisions should be taken at what level is a political question that can't really be decided judicially, so it's up to national parliaments to help define what should be done at the national and European levels. But as Kosmopolito points out, the Yellow Card process is hardly used.
Maybe what the national parliaments need is a stronger institutional link with the EU. If they had an equivalent of the Committee of the Regions that could collate the views of national parliaments and give a joint opinion on legislation, and act as a secretariat that could help national parliaments use their Yellow Card powers more effectively. This could replace the Conference of Community and European Affairs Committees of Parliaments of the European Union (COSAC), which is still a bit too informal to give the national parliaments the institutional support they need at the European level, and use IPEX as a basis. And by publishing joint opinions - or even a summary of the different opinions of national parliaments - this could give a more accessible expression of the different national positions and to the general parliamentary feeling on subsidiarity.
Of course, Member States could go further themselves and use the same system as the Danish parliament to scrutinise national ministers in the Council and give them clear mandates, but that's unlikely to be a popular idea among national governments...