FIFA president Sepp Blatter believes a number of clubs are worried about their own positions following Chelsea's transfer ban.
The Blues have been banned from buying players in the next two transfer windows after being found guilty of irregularities over the move of former Lens teenager Gael Kakuta to Stamford Bridge in 2007.
The London club insist they have done no wrong and are appealing to the Court of Arbitration for Sport in Lausanne.
However, Blatter was in Cardiff on Wednesday to officially open a new Football Association of Wales training complex in the Vale of Glamorgan, and took the opportunity to warn other big clubs that they too could be brought to book.
UEFA president Michel Platini and Blatter have been vociferous in their denunciation of what they have respectively described as "child slavery'' and "child trafficking''. The two governing bodies are seeking to close loopholes under EU law that allow players under the age of 18 to move throughout Europe.
Blatter said: "We have now had a case (Chelsea) to analyse. It has been done by a committee with a judge and representatives of many clubs. That has now been settled. There are clubs now who are looking at their books, some have even announced that a certain player has no contract with them and he is an amateur.
"They have done this to try to make sure that the player does not come under the jurisdiction of congress. The case we have just decided on is one with a player going from France to England.
"But most of the cases we have on our desk are from Africa to Europe or South America to Europe. They are taken at 14 or 15 years old with clubs saying that their parents are going too. But they get put into another family, and what happens to them?
"One out of say 20 has a chance to go on in their career. The others are left, and they need to be protected. There is an age limit in the FIFA statute that stops a player being transferred internationally until he is 18. The European Union is different, it is 16.''
Blatter's view made it clear FIFA are intent on a strong stance on the issue. He said: "We now have a committee where each case is dealt with individually to see if a transfer can be allowed or not. It is the start of greater control of our game.
"It is to protect the young players. I have been asked by officials in Brazil to stop the exodus of their young players. We will do the same in Africa. We are trying to organise leagues so players there can earn a decent living.
"That takes time, but we have started because it is the only way to protect young players. This current issue happened two years ago, I do not know why it has taken this time. But there are so many cases on the desks of FIFA.''