Yes there are regulations you have to meet for a food stall. 

If a Health / Hygiene Certificate is appropriate to your stall, please forward a copy to the Karnival Convenor. 

Additionally, please read the following form http://wellington.govt.nz/~/media/services/consents-and-licenses/food-safety/files/food-stalls.pdf. Complete pages 3 and 4 and send these to the Karnival Convenor with your stall application and Health / Hygiene Certificate.