I realised this has come up here before but ina different discussion, so I went googling.

And somebody had already provided the answer on the mechanisms.

Migeru:

I wonder whether the rest of the council could vote to have their voting rights suspended. There are provisions in the treaties for this, the question is whether the "breach" qualifies as a trigger for those provisions.

European Commission: Consolidated  version of the Tresty on European Union

Article 6

1.   The Union is founded on the principles of liberty, democracy, respect for human rights and fundamental freedoms, and the rule of law, principles which are common to the Member States.
   
2.   The Union shall respect fundamental rights, as guaranteed by the European Convention for the Protection of Human Rights and Fundamental Freedoms signed in Rome on 4 November 1950 and as they result from the constitutional traditions common to the Member States, as general principles of Community law.
   
3.   The Union shall respect the national identities of its Member States.
   
4.   The Union shall provide itself with the means necessary to attain its objectives and carry through its policies.

Article 7
1.   On a reasoned proposal by one third of the Member States, by the European Parliament or by the Commission, the Council, acting by a majority of four fifths of its members after obtaining the assent of the European Parliament, may determine that there is a clear risk of a serious breach by a Member State of principles mentioned in Article 6(1), and address appropriate recommendations to that State. Before making such a determination, the Council shall hear the Member State in question and, acting in accordance with the same procedure, may call on independent persons to submit within a reasonable time limit a report on the situation in the Member State in question.
The Council shall regularly verify that the grounds on which such a determination was made continue to apply.

1.   The Council, meeting in the composition of the Heads of State or Government and acting by unanimity on a proposal by one third of the Member States or by the Commission and after obtaining the assent of the European Parliament, may determine the existence of a serious and persistent breach by a Member State of principles mentioned in Article 6(1), after inviting the government of the Member State in question to submit its observations.
   
2.   Where a determination under paragraph 2 has been made, the Council, acting by a qualified majority, may decide to suspend certain of the rights deriving from the application of this Treaty to the Member State in question, including the voting rights of the representative of the government of that Member State in the Council. In doing so, the Council shall take into account the possible consequences of such a suspension on the rights and obligations of natural and legal persons.
   

The obligations of the Member State in question under this Treaty shall in any case continue to be binding on that State.

1.   The Council, acting by a qualified majority, may decide subsequently to vary or revoke measures taken under paragraph 3 in response to changes in the situation which led to their being imposed.
   
2.   For the purposes of this Article, the Council shall act without taking into account the vote of the representative of the government of the Member State in question. Abstentions by members present in person or represented shall not prevent the adoption of decisions referred to in paragraph 2. A qualified majority shall be defined as the same proportion of the weighted votes of the members of the Council concerned as laid down in Article 205(2) of the Treaty establishing the European Community.
   

This paragraph shall also apply in the event of voting rights being suspended pursuant to paragraph 3.
6.   For the purposes of paragraphs 1 and 2, the European Parliament shall act by a two-thirds majority of the votes cast, representing a majority of its Members.

It is hard to see that there is a breach of paragraph 6, but it might very well be used anyway. If they are really underhanded, of course the humanitarian situation that is a result of the austerity policy can be used to argue that the member state is breaching "the principles of liberty, democracy, respect for human rights and fundamental freedoms, and the rule of law". But to make it stick, they need 2/3s in the EP, and that might be tricky.

I see nothing in there about cancelling voting rights for breaking treaties as such. The Commission could take them to the Court, but max penalty there is (afaik) fines. Also, Sweden is in ongoing violation of the third step of the EMU treaty so it would lock a tad like selective enforcement.

They could be shut out of Eurogroup (not Ecofin) meetings.

Eurogroup - Wikipedia, the free encyclopedia

A formal legal basis was granted for the first time under the Lisbon Treaty when it came into force on 1 December 2009. Protocol 14 of the treaty lays out just two articles to govern the group;

Article 1: The Ministers of the Member States whose currency is the euro shall meet informally. Such meetings shall take place, when necessary, to discuss questions related to the specific responsibilities they share with regard to the single currency. The Commission shall take part in the meetings. The European Central Bank shall be invited to take part in such meetings, which shall be prepared by the representatives of the Ministers with responsibility for finance of the Member States whose currency is the euro and of the Commission.
Article 2: The Ministers of the Member States whose currency is the euro shall elect a president for two and a half years, by a majority of those Member States. --Protocol 14 of the Consolidated Treaties of the European Union (as amended by the Treaty of Lisbon)^[13]

Furthermore, the treaty amended the Council of the EU's rules so that when the full Ecofin council votes on matters only affecting the eurozone, only those states using the euro (the Eurogroup countries) are permitted to vote on it.^[14]

It would however do wonders agaisnt TINA to haev a country on the Ecofin loudly procalim that there are better options after each meeting.

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If they do lose voting rights and get a running tab of fines that is larger then net money they get from the EU, then forming a SEU (with or without a Seuro) could be meaningful as they have effectively been kicked out of the EU. Depends on political logic of course, I suspect there would be a lot against any union.

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