Earlier this month Barcelona wrapped up the La Liga title, with the runners up spot predictably sealed by their eternal rivals Real Madrid. These two illustrious enemies grab the majority of headlines in Spain and it is no surprise that they make up two of the three clubs that have never been relegated from the Spanish top flight. However, the third club is something of a surprise - Athletic Bilbao from the northern Basque region.

Since 1912, Athletic have followed a strict rule of only fielding Basque players. The policy is something of an anachronism in the modern world, where top flight clubs in Spain and England are commonly the ultimate international melting-pots. But despite not having won the league title since 1984, the club still remain competitive with the big boys in Spain - some of the giants of world football.

How can such a policy legally exist in the modern world - and would it be tolerated in the UK? It would seem that refusing to recruit foreign workers (or even those from another part of the same country) would fall foul of a host of regulations - most obviously the Equality Act 2010, under which race, nationality and ethnic origin are protected characteristics, and an employer cannot prefer one person over another because of them. Premier League clubs in both Scotland and England have discussed ways of ensuring a minimum number of homegrown players are represented in their sides - but such discussions have failed to get off the ground, largely due to the inability to make rules compatible with European freedom of movement laws.

Arguably, a policy of recruiting only from one country or region could be found nowhere else in modern Europe. Even in Spain, which has ratified Protocol 12 of the European Convention on Human Rights (forbidding discrimination by any public bodies) it would seem that Athletic Bilbao's policy is vulnerable to a challenge in Strasbourg. However, in reality no such challenge appears to be forthcoming. It seems that in sport, uniquely, the tradition, history and emotion associated with one institution has been able to trump the letter of the law.