Has anybody else had this experience?

I have a client with a .com domain.  It was originally registered
through a certain company that has been the subject of much recent angst
and anger on this list.

I needed to do a re-delegation, so I asked my client to get hold of his
registry key - not only for me to make the change, but for his own
protection as well.  When my client requested the information, he was
told by the "certain company" concerned "We cannot disclose that
information, because if we do you will be able to change everybody elese
domain as well"

My client, in his ignorance, accepted this as a valid reason as to why
he could not get his own registry key.

What recourse does my client have to force the reseller to release the
information?

Ron Stark