The plastic trumpet, whose drone has been likened to a swarm of bees, has become the unmistakable background sound of the World Cup.
The fatwa issued by the UAE's General Authority of Islamic Affairs and Endowments says that above 100 decibels, the buzzing sound of the vuvuzela is "haram", The National newspaper reported Friday.
According to the fatwa, the horns can be used only in stadiums if they pose no harm.
"However, importers and traders must ensure that its power is not over 100 decibels so as to avoid damaging people's hearing," the ruling declares. "The vuvuzelas in the markets now could produce sounds reaching 127 decibels."
Meanwhile, a few traders cancelled orders for more vuvuzelas after they found the horn could be harmfull.
One trader found out that the horns had originally been used by African shamans and witchdoctors. "I searched on the Internet and found some articles regarding it. They were used to bring out devils," he said.