Does a recordkeeper have standing to challenge a summons issued under section 7604 of the Internal Revenue Code?

Section 7604 of the Internal Revenue Code provides, in turn, for the enforcement of an I.R.S. summons through a proceeding in the federal district court, which may use its contempt powers to compel compliance. A taxpayer does not have standing to intervene as a matter of right in such an enforcement proceeding against a party in possession of records of the taxpayer "simply because it is his tax liability that is the subject of the summons." Donaldson v. United States, 400 U.S. 517, 530, 91 S.Ct. 534, 542, 27 L.Ed.2d 580 (1971). Thus, prior to the tax code amendments adopted in 1976, only the recordkeeper, who generally had no stake in protecting the privacy rights of the taxpayer, had standing to challenge claimed intrusions into those rights by the I.R.S.