Italian clubs joining competitions which have not received authorisation by world and European governing bodies FIFA and UEFA will not be allowed to play in national competitions, the head of Italy's football federation (FIGC) said on Monday.
The move comes after three of Italy's top-flight Serie A clubs, Juventus, AC Milan and Inter Milan, were among 12 founding members of a proposed European Super League, which collapsed amid a fierce public backlash.
"Whoever is considering joining a competition which is not authorised by UEFA, FIFA and FIGC will lose its membership," Gabriele Gravina told a news conference.
A spokesman for the FIGC confirmed that clubs joining unauthorised competitions, like the European Super League, will not be allowed to take part in Italy's competitions.
The FIGC council approved a new clause to be inserted into federation rules underlining that clubs registering for national leagues must clearly agree they will not join private, unauthorised competitions, or they will be banned.
The clause also applies to friendly games and tournaments.
The breakaway ESL project, which planned for some of Europe's biggest clubs to leave UEFA competitions but continue playing in national leagues, collapsed within three days amid an outcry from fans, governing bodies and governments.
"Anyone who has interpreted the Super League as a simple act of weakness on the part of some clubs experiencing economic difficulties is wrong," Gravina said.
"At the moment we have no news about who has stayed and who is out of the Super League.
"This regulation will be inserted in the national licences and will then be embedded into the code of sporting justice.
"If, by the deadline for applications to the national championships on June 21, someone joins up to other private leagues, they will not take part in our championship."
On Wednesday, Inter Milan confirmed in a statement that they were "no longer part of the Super League project," but Milan and Juventus have not explicitly pulled out.
Milan indicated their withdrawal by saying in a statement that they "must be sensitive to the voice of those who love this wonderful sport" following fan criticism.
Juventus, whose chairman Andrea Agnelli was one of the driving forces in setting up the new Super League, said they "remains convinced of the soundness of the project."
However, the club also said in its statement that "at present there are limited chances that the project can be completed in the form originally conceived."