Law of conservation of angular momentum is stated as “If the total external torque acting on a body is zero, the total angular momentum of that body remains constant or conserved”. This means that the angular momentum of that body remains same in absence of external torque.
According to the Law of conservation of angular momentum
Angular momentum = I1ω1 = l2ω2= constant
I1 and ω1 are the initial moment of inertia and angular velocity of a rotating body
I2 and ω2 are new moment of inertia and angular velocity of the body