I belive a rule was invented in the wake of Liverpool not making the top 5. An extra place was allocated to Liverpool to make 5 English teams but I believe the 4th place team in Spain had to make way for Reals inclusion. It's the Countries own F.A.s who decide whom enters the competion. The English F.A. stuck by Everton for finishing forth so therefore Fifa and/or Uefa made special dispensation. The rule then was changed that should the holders finish outside the CL places one of those teams that finished inside the CL places would have to make way.