The issue of whether there should be a universal definition of 'independence' has been considered by the International Chamber of Commerce (ICC).
The ICC decided not to provide specific guidelines to prospective arbitrators for fear that they would become too rigid. However Stephen Bond, a former Secretary General of the Court, has described the absence of a "close, substantial, recent and proven relationship" between a party and a prospective arbitrator as the essential feature of independence.
How close is 'close', how substantial is 'substantial' and how recent is 'recent' are all matters of potential disagreement which will inevitably depend on the circumstances of a particular case.