Why can I not procure the shift control mechanism within the transmission on 2007 Mercedes-Benz ML350 4MATIC

The "independent" vehicle service and repair firm I employ has ascertained that a shift control device, within the transmission, is malfunctioning. This is the "good news" as apparently only Mercedes dealers may procure this device, classified as a TRP, (Theft Related Part). In fact owners are not permitted to purchase the device. How is this not a restraint of trade matter?

Asked by for the 2007 Mercedes-Benz ML350 4MATIC
try trans and see if its avail thru them. alot of parts are dealer item only u may have one, this is for security reasons. IT PROTECTS YOU AND YOUR CAR
I genuinely appreciate your response to my inquiry and recourse suggestion. Were I on the California side of the country I'd make a trip to thank you personally.

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