Henry Farrell has the scoop. Excerpt (the post has much more):
…will national parliaments get an effective veto over decisions made at the EU level [?]. The constitutional treaty provided them with a warning role which I suspect would have amounted in fact to an effective veto power (it would be politically difficult to ignore their recommendation) – at the moment, there is a proposal on the table to enhance this further. This seems to me to be an excellent idea. National parliaments have been losing clout in the EU – a lot of their business now involves either rubber stamping or making minor modifications to legislation that is drafted at the EU level. With a couple of exceptions, they don’t play much of a role at all in discussing how governments should negotiate on European legislation. Providing them with an effective veto at the end of the process would mean that they would have to be consulted earlier, and would perhaps become over time a key partner in the legislative process. This would mean increased inefficiencies in getting things done (the addition of another veto player), but would also mean a lot more democratic legitimacy. At the moment, governments are able to get away with a lot of stuff at the EU level that they couldn’t get away with domestically.
My personal view is to keep the extra roadblocks yet deny the extra legitimacy. Ultimately I would have the EU be more like a huge free trade area and "bribe Eastern Europeans to be freer" society. I agree that Henry’s wishes for a more active EU would be good for the short run (elites can be smart), but in the longer run I fear the destabilizing consequences of organizing so many political decisions around institutions which will never connect with voters in any single country or linguistic group.