Broadcasters cannot stop customers using cheaper foreign satellite TV services to watch Premier League football, an EU legal adviser has said.
A non-binding opinion from advocate Juliane Kokott of the European Court of Justice said a block breached EU laws.
Portsmouth pub landlady Karen Murphy, fined for using a Greek service, had argued the EU single market should let her use any European provider.
Sky and ESPN have the broadcast rights to Premier League football in the UK.
Sky has pumped billions into top flight English football since the league was founded in 1992, with the money given to clubs allowing them to buy some of the top names in the world.
The European Court of Justice (ECJ) will make a ruling on the matter later this year.
Ms Murphy said she was "relieved" at Advocate General Kokott's opinion.
The Premier League said it was studying the detail of the opinion but felt it was not compatible with existing EU case law.
It also said that if the opinion was adopted by the ECJ it "would damage the interests of broadcasters and viewers of Premier League football across the EU".
A spokesman added that if the advocate general's guidance was taken it would stop rights holders from marketing their properties in a way which meets the territorial and cultural demands of broadcasters.
They said they hoped the ECJ would uphold current European law, which the league said was "framed to help promote, celebrate and develop the cultural differences within the EU".
The Premier League also said that if the European Commission wanted to create a pan-European licensing model for sports, film and music then it must go through the proper consultative and legislative processes, not use the courts.
'Contrary to EU law'
The case at the European Court of Justice (ECJ) has been about whether a rights holder such as the Premier League can license its content on a country-by-country basis.
Such a set-up has allowed the league to fully maximise the value of its rights.
Although Advocate General Kokott's opinion is not binding, judges usually follow the guidance from the advocate.
If they do, selling sport, movies, or any other content, on an exclusive territory-by-territory basis within the EU may no longer be possible.
"The exclusivity agreement relating to transmission of football matches are contrary to European Union law," she said in her opinion.
"[The] exclusivity rights in question have the effect of partitioning the internal market into quite separate national markets, something which constitutes a serious impairment of the freedom to provide services."
Ms Murphy had been convicted for using the cheaper Greek subscription to show top flight football in her pub.
She used the Nova firm to show matches in the Red, White and Blue pub in Portsmouth as it was less expensive than Sky.
Enforcers working on behalf of Football Association Premier League Limited (FAPL) - the private company which represents the broadcasting interests of the 20 English Premier League clubs - brought the prosecution saying only Sky TV had exclusive rights to show its games in the UK.
She had to pay nearly £8,000 in fines and costs.
Industry experts say satellite broadcasters face having to reform - leading possibly to the creation of just a handful of pan-European broadcasters.
It was pressure from Brussels which forced the Premier League to offer its live matches to more than one broadcaster, rather than just renew the exclusive deals it traditionally had with Sky.
Packages were consequently taken up by Setanta, and when they went bust, by ESPN.
Meanwhile, Smithfield Partners is a law firm which represents QC Leisure, David Richardson and SR Leisure Limited, all of whom are defendants to a civil action brought by the Premier League.
The defendants are publicans and businesses importing decoder cards into the UK from other member states within the EU.
Like Ms Murphy, these defendants have been waiting for a ruling in this matter since the case was referred to the ECJ by the High Court in June 2008.
"We are very pleased with the opinion of the advocate general and are confident that the ECJ will endorse the same reasoned legal analysis in their judgement later this year," said Martin Ochs of Smithfield Partners.