From the thread title:
Something needs clarification here.
If he is playing a "popular movie song", it IS copyright infringement to publish his performance without obtaining permission from the copyright holder. It does not matter if it's his own arrangement of the music; copyright applies to derivative works.
On the other hand, if it's a completely original composition that merely happened to have the same name, you'd have a case for contesting the infringement claim.
Get advice from a lawyer who is experienced in these matters. The last thing you'd want would be to end up with a "let's make an example of him" lawsuit on your hands.