Civil Guard officers patrolling the popular festival last year, which featured folk musicians from across the world, were astonished to hear three men offering drugs to the public.
The men were arrested and found to be in possession of 14 ecstasy tablets and a plastic freezer bag filled with marijuana buds. They also had precision scales and €761 ($986) in cash.
One of the men, a foreign resident, was declared a flight risk and placed in preventative custody. The three later told a judge that the megaphone announcement had been a joke and that the drugs were for their personal consumption.
He did not believe them and the men now face trial.
According to local daily La Voz de Galicia, prosecutors are seeking penalties of up to four years imprisonment for the hawkers.