As far as I understand it, the Panoz/ACO American/European/Asian etc. Le Mans Series can only call itself a 'world' championship if it gets itself governed by the FIA, and of course the FIA (this year) is running (or endorsing) its own GT and Sportscar series.
Of course, it would be much easier if Don Panoz and John Magoletsi sat down and agreed on a common set of rules and regs and initiated a single championship for both GT and sportscars. A single series would make it easier to fans to keep track of, gain extra media coverage thus bringing more finance into the sport and everyone is a winner.
This of course will never happen.
