This will be a legal requirement to satisfy some kind of health and saafety regulation.

I am turning sausages at the BBQ at my 5 year old daughters school fair, but am only allowed to do so as I have recently completed a food hygiene course.

It protects the organizers from liability.

What you need to do is find out what the legal standards are and show that your stall or whatever it is doesn't contravene the minimum standards.

I would check up with your local health and safety body - pehaps even find the right website and print out the rules, and make sure you comply with them.