The foreign ministers of the four countries said in a joint letter to European Commission President Jose Manuel Barroso, obtained by The Associated Press on Friday, that the bloc must be "extremely watchful" whenever its fundamental values are put at risk.
The EU "must be able to react swiftly and effectively to ensure compliance" with the bloc's basic principles if a member country is seen as backsliding, including a last-resort option to cut EU funding to offenders, they said in their message.
The letter didn't name any countries, but EU officials in the past have expressed concern about legal changes or lax enforcement, especially in Romania, Bulgaria and Hungary.
A new mechanism should allow the European Commission to intervene in an early stage and require the country to remedy the relevant law or situation, provided the step is also backed by a majority of EU states, the ministers proposed in their letter dated Thursday.
The European Union is able to fine companies under its antitrust rules, but the 27-nation bloc is largely powerless if one of its member states changes its laws to curb the rule of law or democracy itself.
Referring to ongoing negotiations on possible EU accession talks with several Balkan nations and Turkey, the four nations' foreign ministers also said that they believe that once a mechanism is in place it could help secure public support for further enlargement.
The European Commission's spokesperson welcomed the letter, noting that Barroso had in the past called for a similar initiative.
"We have quite exact rules and mechanisms in the union which are used to examine questions of rule of law in countries applying for membership. But after states are members, there are not really any established mechanisms to examine the situation and intervene if necessary," Finnish Foreign Minister Erkki Tuomioja told Yle on Saturday.
"At this stage, it is not worthwhile listing any countries. There can be these kinds of problems in older member states, too, even in founding member state. The issue is that there should be the kind of mechanisms, means of examining, and in extreme cases the opportunity for sanctions, as well, if these core principles are not adhered to in all member states," said Tuomioja.