http://www.cadc.uscourts.gov/internet/opinions.nsf/20B08E3F3940921E85257CFD004EF672/$file/13-1090-1498618.pdf 
Michael H. Lubetsky of Davies has been kind enough to provide the following commentary (I am indebted to Guy Du Pont, Ad. E., for initiating the collaboration):
The “United States Tax Court” (“USTC”), like the Tax Court of Canada (“TCC”), originated as an administrative “board” and was later reconstituted into a “court of record” with “judges”. Constitutionally, however, did these initiatives actually transform either tribunal into a bona fide organ of the judical branch of the government, or did they remain essentially organs of the executive? The answer to this question can have, inter alia, a particular impact upon the inherent powers of Court as well the procedures that must be followed to remove a judge from office.
Kuretski et al. v. Commissioner of Internal Revenue Service (June 20, 2014 – 2014 #13-1090) was a decision of The United States Court of Appeals for the District of Columbia Circuit (the “DC Circuit”) where taxpayers did not pay their taxes and were eventually assessed by the IRS. After losing their case before the USTC, the taxpayers sought to vacate the decision on the grounds that the power of the President to remove a USTC judge “for inefficiency, neglect of duty or malfeasance in office” violated the constitutional separation of powers and rendered the USTC decision a nullity.
This removal power, which has never actually been used, is a relic of the day when the US Tax Court was known as the “Board of Tax Appeals” and was unquestionably an organ of the executive rather than the judicial branch of government. As documented in
Kuretski, the Board of Tax Appeals was renamed the “Tax Court of the United States” in 1942, and then reconstituted in 1969 as a “court of record” “under Article I of the Constitution of the United States”. Throughout the evolution, however, the President’s removal power remained untouched.
Ultimately, in its decision issued June 20, 2014, the DC Circuit held that the USTC, notwithstanding its name and the fact that it exercises “judicial powers”, is not an organ of the United States judiciary, but rather one of the executive:
To our knowledge, this is the first case in any court of appeals to present the question of whether 26 U.S.C. § 7443(f) infringes the constitutional separation of powers. We answer that question in the negative. Even if the prospect of “interbranch” removal of a Tax Court judge would raise a constitutional concern in theory, there is no cause for concern in fact: the Tax Court, in our view, exercises Executive authority as part of the Executive Branch.
[Much of the decision is devoted to distinguishing itself from the Supreme Court of the United States (“SCOTUS”) decision in Freytag v Commissioner, 501 US 868 (1991), a case involving the power of the Chief Judge of the USTC to appoint special judges. Under Article II of the US Constitution, the Chief Judge could only enjoy the power to appoint special judges if either (a) the USTC was a “Court of Law” or (b) the USTC was a “Department” of which the Chief Judge was its “Head”. Although the judges of the SCOTUS unanimously agreed that the Chief Judge had the power to appoint special judges, they sharply divided, 5-4, on whether to ground this power in the fact that the USTC was a “Court of Law” or whether the Chief Judge was the “Head” of a “Department”.]
Kuretski illustrates a fundamental difference between Canada and the United States in its conception of where the executive branch ends and the judicial begins under their respective constitutions. The United States Constitution distinguishes between “Article III Courts”, which include
“one supreme Court, and in such inferior Courts as the Congress may from time to time ordain and establish”, and “Article I Courts” (or “legislative courts”), which are created by Congress pursuant to its power under Article I, §8, c. 9
“To constitute Tribunals inferior to the supreme Court”. [In addition, the US Constitution recognises “Article IV” courts, which apply in some territories under the direct rule of the United States federal government.] The United States Constitution expressly provides that the judges of Article III Courts enjoy tenure and fixed salaries, but contains no such provisions for judges of Article I Courts, which (like the USTC) remain essentially organs of the executive branch.
In Canada, sections 96-101 of the Constitution Act, 1867 concern the “Judicature”, with section 101 empowering Parliament to “
provide for the Constitution, Maintenance, and Organization of a General Court of Appeal for Canada, and for the Establishment of any additional Courts for the better Administration of the Laws of Canada.” The TCC being constituted pursuant to section 101, is uncontroversially considered part of the Canadian “judicature”. Although the Constitution Act, 1867 only expressly provides tenure for the judges of the “Superior Court”, the jurisprudence in Canada has largely extended the requirement for tenure (as well as fixed salaries) to judges of all “courts” (including, presumably, the TCC). See e.g.
Ref re Remuneration of Judges of the Prov Court of PEI; [1997] 3 SCR 3 ¶107-109. This has not happened in the United States; where the judges of Article I Courts typically have limited terms and less institutional independence, and where the jurisprudence has reacted not by extending guarantees of judicial independence to the Article I Courts, but rather by circumscribing their powers.
Ultimately, the limited independence and powers of Article I Courts in the United States confirm that they correspond more to what in Canada are known as “federal administrative tribunals” rather than courts. Consequently, the reconstitution by Congress of the “Board of Tax Appeals” as an “Article I Court” represented a far less significant transformation that what occurred in Canada in 1983 when the Tax Review Board was renamed the TCC and constituted a court of record:
3. The Tax Review Board, established by the
Tax Review Board Act, chapter 11 of the Statutes of Canada, 1970-71-72, is hereby continued under the name of the Tax Court of Canada as a court of record. 1980-81-82-83, c. 158, s. 3.