For me, it is unnecessary to regulate hunting it is because it makes species of animals endangered and extinct. It will decrease the number of animals living in the area and eventually, the animals will disappear.
But, if that statement is changed into a fact, and I am asked, "Why it is necessary to regulate it?", then, this is my answer: (if this a fact) (just an example)
It is necessary to regulate hunting because it might make the ecosystem more balanced especially if the animals hunted are those ones that have greater numbers. If there is no hunting, then there will be more predators, which means, that the animals below them will lose their numbers. That might be the answer why it is necessary to regulate hunting. (even though I am against that...)