FIFA's 'six-plus-five rule' would be incompatible with continental law, the European Union reiterated today.
The rule would limit the number of foreign players in each club's starting line-up to five and president Sepp Blatter hopes to have it in place by the 2012/13 season.
But EU spokesman John MacDonald stressed it would fall foul of the EU's anti-discrimination legislation and would not stand up in court.
'The 'six plus five rule' of FIFA is simply a rule that is based on grounds of nationality so that is incompatible with community law,' he told Sky Sports News.
'If they were to implement the 'six plus five rule' in Europe what would happen is any professional football player who feels aggrieved by the rule would be able to take the football club concerned to court and he would probably win the case.'
FIFA have said they want to 'explore' the possibilities 'within the limits of the law', but while the EU would welcome dialogue, MacDonald does not see a way forward for the plan.
The EU are, however, positive about a proposal from Europe's governing body UEFA that would set a quota for players trained in a particular country but not necessarily of that nationality.
'We have had valuable exchanges with UEFA in the past,' MacDonald continued. 'FIFA have been less forthcoming with dialogue but we welcome the desire now, that has been expressed by FIFA, to come and talk about these issues.
'In a study we did of the home-grown players' rule, we're of the opinion - on the basis of current evidence - that in fact that rule neatly side-steps the problem of direct discrimination, which is against community law, and can be considered to be compatible with community law.
'Any indirect discrimination is justified by the aims, which are to bring balance to the game through encouraging the development of young football talent.'
Former England manager Steve McClaren believes legislation is the wrong way to address the problems in the domestic and international game.
McClaren oversaw England's failed bid to qualify for Euro 2008, and the diminishing number of English players in the Premier League was widely believed to have contributed to that failure.
He said: 'People are trying to change (the percentage of English players) through legislation, through quotas.
'I can see that concept but the main one I'm concerned about is improving our players and improving our coaches because if you do that you've got a long-term plan.
'At present we haven't got any British coaches working abroad and that's where you get your education.
'We've imported it in, through players first and managers and coaches after that and eventually, if we're not too careful, we're going to produce a Premier League full of foreign coaches, foreign owners, then where do British coaches come through and manage?'
EU sports commissioner Jan Figel revealed proposed sports legislation could be considered as a special case - but only if it is non-discriminatory.
'What we promote - and what we want to further increase - is specificity, which is not the same as exclusivity of sport,' he told Sky Sports News.
'Specificity means what is not business as usual. Therefore we need, on a case-by-case basis, to look into relevant issues, problems or questions and we are ready to do that.
'Specificity not exclusivity is my message to FIFA, UEFA and other partners, and we will even more strongly be able to use specificity of sport because in the new treaty there is a sport article included for the first time which mentions specificity of sport being taken into account.'
Figel singled out the case of Jean-Marc Bosman in 1995, which ensured freedom of movement for footballers, to illustrate sport cannot operate outside EU laws.
'There are good ideas or arguments with pros and cons, and one of the strong arguments against is that it violates EU valid law,' added Figel, who plans to speak to Blatter.
'We have in the past combined actions or rules that are non-discriminatory but also fruitful for corporations, for training, for protection of minors, for promotion of sport values, participation in sport starting from early life and lifelong.
'I'm certain together we can find more answers by corporation dialogue, openness, transparency. These are very important principles for all around the table.'