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?"
Professional Footballers' Association chief executive Gordon Taylor believes Fifa's proposal is "tilting at windmills" and believes a balance must be struck between their 'six-plus-five' idea and Uefa's 'homegrown players' scheme, which has already secured politicians' backing.
Uefa defines 'home-grown players' as team members who, regardless of age or nationality, have been trained by their club or by another club in the National Association for at least three years between the ages of 15 and 21.
The Commission has approved the Uefa arrangement because, says Brussels, it contains no player conditions based on nationality.
Taylor believes that idea is more sensible and would like to see that strengthened, admitting it is currently "weak as water".
The players' union chief told PA Sport: "I just feel with the the proposal, it is tilting at windmills in the shape of the European Commission because the law will not allow it.
"That is why I feel that rather than do that as a gesture that may not succeed, there is a much more realistic chance of success in encouraging youth development if they look towards strengthening the already-accepted ruling of Uefa, which albeit is eight out of 25 in a squad as long as they have been developed by a club or country for three years between the ages of 15 and 21.
"That is too weak because it is just in a squad, but if it was then revised to be on the field of play, all clubs would be abiding by the same rules and it would be an encouragement of youth development irrespective of nationality."
Taylor added: "Whilst people say 'they will just bring over youngsters from abroad' they may well do that, but at least they would all have to prioritise youth development.
"With the 'eight out of 25', the European Commission cannot reject that, it is so obviously an encouragement of youth development.
"But it is not enough, it should be talking about a limited number on the field of play because as it stands, it is weak as water.
"It is a case of finding a balance between that, which is too diluted, and Fifa's, which has no chance because of European Commission law.
"We might as well start dealing with reality, and what is achievable."Reuse content