As for the gelatine derived from Halaal animals that have not been slaughtered according to Islamic rites, there is a difference of opinion among Ulama with regards to whether it is Halaal or not.
This difference is primarily based on two issues
1. Whether the gelatine derived from the hide of an animal becomes halaal after the hide is tanned or not.
2. Whether gelatine has been completely transformed from its original state and has satisfied the Sharia requirements of such transformation or not.
Based on these differences, it is best to abstain from such gelatine. However one should not impose one’s view on others in light of the difference of opinion.