In Tennessee tax disputes, the Commissioner of Revenue traditionally is represented solely by the State Attorney General’s Office – that is, until recently when the Multistate Tax Commission (MTC), the national organization for state tax administrators, sought to participate in two related tax cases as counsel of record for the Commissioner. Pfizer, Inc. v. Farr, Commissioner of Revenue and Pharmacia, Inc. v. Farr, Commissioner of Revenue, Davidson County Chancery Court Nos. 09-1945-II and 09-1946-II. Although the State of Tennessee is not a full member of the MTC’s Multistate Tax Compact, it is an associate member, which means that Tennessee participates in and cooperates with the MTC and its member states. The State’s recent effort to bring the MTC on-board as co-counsel for the Commissioner in the Pfizer lawsuits, signals a significant departure from long-standing practice in Tennessee that the only proper parties in Tennessee tax disputes are the Commissioner, represented by the Attorney General’s Office, and the taxpayer, represented by its counsel. In the past, interested third parties have attempted to intervene in pending tax lawsuits, but such efforts routinely have been rejected by the courts, largely – and ironically – based on the objections of the Commissioner and the Attorney General’s Office.