The Lisbon Treaty introduced the "early-warning mechanism", with national legislatures assigned the right to monitor whether initiatives for EU laws comply with the principle of subsidiarity. Does the mechanism really empower national parliaments by giving them a collective veto in EU politics or will it remain largely unused by domestic MPs? This paper leans towards the latter interpretation, arguing that the whole mechanism was mainly introduced in response to legitimacy concerns. It is a rather harmless procedure, with only a marginal impact on the EU´s legislative process. The incentive structure simply works against individual MPs, political parties or parliaments making active use of this instrument. When placed in the larger context of the role performed by national parliaments in EU politics, the early-warning mechanism can be seen to reinforce the perception of domestic MPs acting as the "gatekeepers" of European integration.