One thing we noted about the U.S. Tax Court is that cases from that court are appealable to federal courts of appeals all over the country. Appeal from a Tax Court decision lies in the circuit in which the taxpayer lived when the taxpayer filed his, her, or its petition (complaint) in the Tax Court. (The appeal venue can be changed by stipulation of the taxpayer and the IRS, but that's the general rule.)
This makes the life of a Tax Court judge a bit challenging. If there is a conflict among the courts of appeals on a tax issue, the Tax Court needs to know to which circuit its decision is going to be appealable. For that reason, one of the things the taxpayer has to include in the petition is a statement of the taxpayer's place of residence.
And that means that the Tax Court may have to rule one way or another depending on where the taxpayer lives, treating taxpayers from different parts of the country differently. For example, let's say that on a particular tax issue, the Ninth Circuit favors the IRS but the Fifth Circuit favors the taxpayer. And let's say that the Tax Court, if left to its own decision, agrees with the Ninth Circuit. If a taxpayer comes in from the Fifth Circuit, the Tax Court will have to apply the Fifth Circuit rule, even though the Tax Court thinks it's wrong. The Tax Court doesn't have much choice in the matter -- it will be reversed by the Fifth if it does what it thinks is right -- and so it has to buckle under. If a taxpayer comes in with the same issue from the Ninth Circuit -- or a circuit in which the court of appeals has not yet spoken -- the Tax Court can and will do what it thinks is the right thing, and on these facts hold for the government.
There's a famous 1970 Tax Court case that lays out the rules of the road here. It's Golsen v. Commissioner, 54 TC 742 (1970) (aff'd on other grounds), and for Pete's sake, it even has its own Facebook page! I went ahead and gave it a "Like."