Actually they tried the normal way, where they didn't shoot and asked the poachers to surrender / tried to arrest them. But the rangers would get shot and the animals would continue to get poached.

Seeing this as a problem, a new executive order / law was passed allowing shoot at sight orders at national parks / protected zones.

Poaching has reduced, the number of rangers getting shot has reduced. The number of poachers getting shot has reduced (they don't wanna fuck around anymore).

Overall it has increased peace.