South American talents such as Luis Suarez and Marcelo have been La Liga mainstays for Barcelona and Real Madrid respectively, but the fact that they are even playing in Spain at all is seen as fortunate.
La Liga have strict rules about how many non-EU players are allowed to play for each side, which obviously affects the way a club handles their transfer business if they are looking to coup players who do not hail from Europe.
So what is the rule, why is it enforced and how do players and clubs manage to work around it?