bocadillo
Water Gypsy
Can the referee actually order that? I thought that was one of those things that he could only comment about in his report but should have no influence over while the game was in progress.
Yes, he can. Quite apart from the specific instructions that referees have been given regard 'multi-ball' use, the Laws of the Game state that the ball may not be changed during the match without the authority of the referee.
The guidelines actually encourage the use of multiple balls in order to spped up the game, but they are equally clear that they must be used fairly and not interfere with play.