One owner of a "joint owner" box is deceased. The other owner, who lives out of state, is not the executor of the estate. The executor of the estate has a key and wants to remove the contents of the box with a court order. is this permissable?

First, they don't own the box, they rent it.

Whether a joint renter can still enter the box after the other renter has died is a matter of 1) state law and 2) the terms of the lease they signed. The second question (answered by the same sources) is whether a duly appointed representative of the decedent's estate has a right of access to the box.

You may want to consider re-posting your question in your state's forum, but it's still important to review the terms of the lease.

Thank you, and I do understand that the box is rented, not owned.