The national parliaments of EU member states have an "early warning mechanism" whereby if one third raise an objection – a "yellow card" – on the basis that the principle of subsidiarity has been violated, then the proposal must be reviewed. If a majority do so – an "orange card" – then the Council or Parliament can vote it down immediately. If the logistical problems of putting this into practice are overcome, then the power of the national parliaments could be deemed an extra legislature, without a common debate or physical location: dubbed by EUObserver a "virtual third chamber".