A court in Haarlem ruled that because Johan Cruyff, one of the club's five commissioners, was not consulted about the decision taken by the other four, it could not go ahead.
Instead, the judge ruled, the decision was on hold for three months until the club's shareholders meet and vote on the issue.
A rift has opened up between Cruyff, now a board member but revered as Ajax's greatest ever player, and the others who include former Dutch international Edgar Davids.
Cruyff has developed a plan to rejuvenate Ajax's famous youth training programme with former players including Dennis Bergkamp, Ronald de Boer, Jaap Stam and Marc Overmars playing a leading role as trainers in the academy.
Cruyff and his training team believe Van Gaal, the former Ajax and Dutch national team coach, would not follow the technical blueprint which Cruyff says forms the foundation of leading the club back to the top of the European game.
As a result, Cruyff does not want Van Gaal, sacked as Bayern Munich manager in April, to return to the club.
The court decided that the naming of Van Gaal and also Martin Sturkenboom as directors was legal though the judge suspended the decision for three months to give shareholders the chance to back Cruyff's plans for the club, or those of the other four board members.
Ajax won three European Cups in the early 1970s when he was playing, but their last success came in 1995 when Van Gaal was manager.
