Angular momentum L is defined by summation of mrxv about a certain point. For a rigid body that rotate about an axis that is not the axis of symmetry, in general the direction of L is keep on changing. Also we get different L if we take about different point. Iω is constant for constant ω and I is summation of ∫r2dm where r is the perpendicular distance between the element and the rotation axis. This value is constant even the rigid body is rotating about an axis that is not the axis of symmetry, in contrary with the above argument. What is the restriction for using Iω as the value of angular momentum?