That could be a tricky legal question. The current law is that changes in the line of succession must be approved by all 15 Commonwealth realms. But this law was itself a regular statute passed by the Westminster parliament.
The principle of parliamentary supremacy demands that no parliament may bind the will of a future parliament. That is, could Westminster just override the 1931 statute when they pass this special "cut out Andrew" bill? There might not be a whole lot that says they can't.
That painting should be old enough to be in the public domain. (Although photographs thereof get their own copyright terms.)