Jorge Lorenzo has been told he cannot take part in MotoGP championship leader Valentino Rossi's Court of Arbitration for Sport hearing into a grid penalty imposed for the season's final race.
Rossi, who leads Lorenzo by seven points, clashed with Honda's reigning champion Marc Marquez, who came off his bike in Malaysia last week.
He was demoted to the back of the grid for Sunday's race in Spain.
Lorenzo asked to participate in the appeal but was denied by Cas.
Nine-time world champion Rossi wants the penalty at least suspended for the race in Valencia, the home track of Yamaha team-mate Lorenzo, 28.
The 36-year-old is expected to learn the outcome no later than Friday.
Lorenzo, who won the most recent of his two titles in 2012, finished second in Malaysia and is the only rider who can deny Rossi the championship.
Rossi must finish second if Lorenzo wins Sunday's race in order to secure the title.
Honda alleged Rossi's actions caused Marquez to crash, highlighting data they said showed his front brake lever received a sudden impact that locked the front tyre, but Yamaha said that was "not proven".