I know in Vic they have really strict guidelines for selling food at markets etc. The amount of paperwork and things you need to do while there is amazing.

One form alone is 20+ pages and that's just a sausage sizzle etc.

Someone also has to have a food handlers cert and with bigger functions someone has to have a higher cert (cannot think of it's name).

We have to have an ABN for our functions and be registered with the council.

If they are selling regularly they should have all these and the registration should be on display.

If you are unsure you can contact your council to find out if they are registered.