I believe true halal gelatin is vegetarian (here's what I found out about that):
"Theres this type of halal gelatine called 'Agar Agar', its mainly used by Asians. We use it at home instead of gelatine its derived from seaweed... but its very strong so you only need to use a little bit otherwise the jelly ends up really hard! Umm... i think you can find it in supermarkets"
but here's a comprehensive site where you can research and even email them to be sure:
http://www.halalgelatine.com/
Good luck!