Helmets are not obligatory in Andorra, however they are always recommended. If you don't want to go to the expense of buying your own you can rent them here: arinsal.co.uk/shop/arinsal/ you'll find them under the "extras" tab.
Hope that helps, just ask away if you have any more questions.
A group of 4 of us , 3 skiers and a boarder are coming out to the resort on the 29th of december and cannot wait, 2 of the group are in ski school and theothers are just skiing for the week. The Chat has turned to helmets, what is the stance on them in Arinsal.andorra as i know they are compulsary in USA and Canada?