If the part has been legitimately fitted, under the terms of an agreement, then I would have thought Emirates would be entitled to refuse Delta access to it, once fitted and to have asked for police aid if necessary. It may still have needed to be signed off but I would have thought a Boeing engineer, with a telex from the DGCA UAE, could have done that? May have been wise to include the FAA as well. Much more to this than meets the eye I suspect.