Treasury checks are not allowed via mobile deposit as a matter of institution preference, correct? I don't think that the Treasury prohibits the electronic imaging, it seems to be that since Treasury checks follow their own rules for returns, that the institution wants to physically view the check prior to deposit.

Is anyone aware of a rule that actually says you cannot deposit Treasury checks via RDC or mobile deposit?

Thanks!

Any such rule is, as you have suggested, a creature of the financial institution with the RDC contract/agreement.