Does the EU have the power to expand its own power without the consent of EU members? If yes, what is the legal framework that allows it to do so? If not, what do the EU members have to do to allow the EU to have more power over its members, and can the people of the member countries vote for or against it? I've heard people say that the EU was a political scheme to allow powerful people to obtain undue power by centralizing the political power into one single entity.
The powers of the EU are defined by the Treaties of the European Union, the most recent of which, the Treaty of Lisbon, was signed in 2007 and came into force in 2009. An enlargement of the powers of the European Union would require a change to the treaties. As with any other treaty, it must have the approval of all concerned countries (28 as of this writing) before it can take effect.
Ratification of a treaty by a member state is subject to the constitutional requirements of said state. In the case of the Treaty of Lisbon, 26 of the 27 member states ratified it through their Parliaments.
Ireland was the only member state to put ratification of the Treaty of Lisbon to a referendum (or two), as in that country it required a constitutional amendment.
Croatia, which joined the EU after the Treaty of Lisbon came into force, put the ratification of its accession treaty to a referendum as well.
In the event that the United Kingdom were to reverse its decision to withdraw from the European Union, future treaty changes would be subject to a referendum in that country under the European Union Act, 2011.
The broad areas of European Union legislative competency are defined by treaty (international agreement) and are decided unanimously by "Revision Procedure". In this area, therefore, the heads of government of each member state must consent.
There is an important distinction to be made here between the peoples of each member state and the heads of government. EU treaty law is a unique kind of legislation: it is legislation passed by a domestic legislator, to enable a legislature in another country to legislate on their behalf.
In effect, your representative - usually a cabinet member, nominally delivering a platform you had a vote on - is using the power you lent them to transform the democratic nature of the very democracy that elected them. A kind of meta-lawmaking.
Once an EU treaty change has been made, this requirement for unanimity, in effect, binds the hands of future domestic governments by making undoing or reforming the treaty so difficult as to be nearly impossible.
The domestic electorate can then no longer easily direct reform in the delegated area. From then on, the electorate have been effectively disenfranchised (for the purposes of reform) by their own elected representative.
This is important because democracy is about choice. If the electorate want permit a treaty change in 2005, there might be very good reasons for them to want to undo or reform that change in 2019.
But, after a competency is delegated by treaty, the electorate have no easy way of directing reform of the change.
Prior to the delegation of the competency, or if they were not members of the EU, they could simply un-elect a Government platform and elect a new one.
After delegating a competency to the EU, even if the electorate vote in a new Government platform, the new Government cannot change the law without the agreement of 27 other countries.
In effect this design is a "legal ratchet." A one-way street that encodes the principle of "ever closer union."
Democracy is about exposing real choice (kratos/power) to the demos (ordinary people).
If you have a one-way street on which the common people cannot command "Stop! Please turn around and choose a different route", you don't have a democracy.
Furthermore, this design can be used as a convenient excuse for not addressing the needs of the electorate ("Sorry! The EU won't let us!"), diminishing the democratic character of the country and delivering a pressure-cooker of sentiment without a democratic release valve.
Within the broad areas of delegated competency, the European Union operates on a principle of pooled sovereignty, with the majority of law being subject to majority votes (ie. not unanimity).
In these areas, therefore, legislation can (and is) passed that individual member states do not want because the relevant majority of others do.
A question in the comments forced me to examine more carefully the nature of the "ratchet" in the design of the EU legislature.
A ratchet is, in effect, a one-way valve. It is the embodiment of a power asymmetry.
In the EU this asymmetry exists between two consensus-forming groups:
CG1, the governors (here, the Westminster/EU27 dyad) and
CG2, the governed in a member state (here, the UK electorate).
In the EU, if there is a consensus within
CG1, then treaty change may be driven by virtue of incumbent power.
If there is a countervailing consensus within
CG2 then legislative change may not be driven, by virtue of the absence of EU27 acquiescence, and their positioning outside the democratic reach of
In a democratic system outside of the EU the entirety of
CG1 exists within the democratic reach of
CG2, and so
CG2 can replace
CG1 with a new governor-consensus-group with unilateral reform authority after-the-fact.
In a a democratic system inside EU this cannot happen (the EU-27 sit outside our democratic system), and so reform driven by the governed, in the absence of
CG2 consensus, is impossible.