delivered the opinion of the Court.
The issue in these cases is whether a trustee in the course of administering its fiduciary obligations is en
*392
titled to rely on a directly relevant decision of this Court which has neither been overruled nor questioned. The Court of Claims ruled that the United States breached its fiduciary duty by failing to resist payment of Oklahoma’s estate tax on certain trust property held by the United States acting as trustee for the benefit of the Osage Indians. The Court of Claims recognized that this Court, in
West
v.
Oklahoma Tax Comm’n,
I
The facts and legal background of this dispute may be briefly stated. Before 1906, the Osage Reservation was held in trust for the Osage Tribe by the United States. 1 In that year, the Osage Allotment Act, 34 Stat. *393 539, was passed, which divided tribal land equally among members of the Tribe. However, an individual Indian was not permitted to alienate the land unless “the Secretary of the Interior, in his discretion, . . . [issued] . . . a certificate of competency, authorizing him to sell and convey any of the lands deeded him by reason of this Act.” 2 34 Stat. 542. 3 In addition, the Act created so-called “headrights” which are each tribal member’s individual share of the income derived from the minerals located on the land. The minerals and this income were to be placed in trust for the individual tribal members, subject to periodic distribution from income, until 1984, when legal title to the minerals together with the accumulated income would vest in the individual Indians. 4 Various tribal funds were also placed in trust until that year. As amended, the Act provides that land and funds which are either restricted or held in trust “shall not be subject to lien, levy, attachment, or forced sale . . . prior to the issuance of a certificate of competency.” 61 Stat. 747.
The decedent in this case, Rose Mason, was an Osage Indian who had not received a certificate of competency. Pursuant to the Osage Allotment Act, the United States held certain of her property in trust for her. Upon
*394
her death intestate, an Oklahoma estate tax return was filed which included in her gross estate these trust properties. The Federal Government then paid Oklahoma some $8,087.10 in estate taxes out of the trust properties. Although the decedent’s administrators were discharged in 1968, in 1970 the estate was reopened for the purpose of permitting the administrators to challenge the United States’ payment of the tax. A suit was filed in the Court of Claims alleging that the United States had breached its fiduciary duty in making the payment,
5
and that court upheld the claim together with the United States’ third-party claim against Oklahoma. See
II
In
Oklahoma Tax Comm’n
v.
United States,
As the Court of Claims itself recognized, the
West
decision “applied to the very type of trust property now before us.”
It must be noted, however, that the
Squire
Court did not purport to question or overrule
West,
and, indeed, did not so much as mention that decision. The
Squire
case involved a different tax by a different level of government on the trust properties of a different tribe held pursuant to a different statute. As the
West
decision itself made clear, decisions relating to other types of taxes are not readily transferable to the area of estate and gift taxation where the tax is imposed on the transfer of property rather than on the property itself or the
*396
income it generates. Cf.
Plummer
v.
Coler,
Nor can we agree with the Court of Claims that the foundations of
West
have been substantially weakened by subsequent lower court decisions. Apart from our difficulty in comprehending how decisions by lower courts can ever undermine the authority of a decision of this Court, we think it clear that each of the cases relied upon below is distinguishable from
West.
Thus, while it is true that the Ninth Circuit construed the Mission Indian Act, 26 Stat. 712, to invalidate California’s estate tax as applied to a California Mission Indian in
Kirk-wood
v.
Arenas,
Thus, as the Court of Claims itself conceded, “since the
West
case in 1948, there has been no holding exactly on the precise issue now before us — the liability of such Osage property to state death taxation.”
We need not decide, however, whether in a case squarely presenting the issue, we would continue to adhere to
West.
For the issue in this case is not whether
West
should be overruled, but rather whether the United States breached its fiduciary duty in failing to anticipate that it would be overruled. Cf.
Helvering
v.
Griffiths,
*398
When the question is so posed, we think that the answer is obvious. There is no doubt that the United States serves in a fiduciary capacity with respect to these Indians and that, as such, it is duty bound to exercise great care in administering its trust. See,
e. g., Seminole Nation
v.
United
States,
Applying these familiar principles to the facts before us, we are required to decide whether the United States can be said to have acted with less than the requisite care in refusing to contest the Oklahoma tax. When the State asserts a doubtful tax claim against trust property, the trustee is often presented with a close question. Normally, the trustee is obligated to pay taxes on the trust estate, and, indeed, if he negligently fails to do so, he may be held liable for any resulting penalty. See, e. g., 2 Scott 1422. Yet, as these cases demonstrate, if he pays the tax, he may similarly be called upon to reimburse the trust estate for the amount of the tax.
In order to avoid placing a trustee on the horns of this dilemma, most courts which have considered the problem have given a trustee broad discretion to pay taxes claimed by the State so long as the trustee’s judgment that the taxes are valid or that the costs and risks of litigation outweigh the advantages is not wholly unrea
*399
sonable. See,
e. g., Crutcher
v.
Joyce,
Thus, even if the
West
case had never been decided, the plaintiffs below would still have had difficulty in making out a case that the United States had breached its fiduciary duty by paying the tax. But, of course,
West
had been decided at the time the tax was paid, and we therefore deal here with an assertion of taxing authority which was not merely plausible but had been expressly approved by a decision of this Court. Generally, when a trustee is in doubt as to what course to pursue, the proper procedure for him to follow is to conform his conduct to the instructions given him by the courts. See,
e. g., Mosser
v.
Barrow,
It is, of course, true that Supreme Court decisions are on occasion overruled and that the opportunity to overrule them would never arise if litigants did not continue to challenge their validity. But, in this context at least, it is unnecessary to penalize the United States’ proper reliance on our past decisions in order to re-examine them, since there is no bar to a suit by plaintiffs below directly against Oklahoma for recovery of the tax. Cf.
Poafpybitty
v.
Shelly Oil Co..,
We do not have to say that a fiduciary may never be held liable for reliance on prior decisions of this Court. But, as the discussion above demonstrates, the United States’ reliance on West was reasonable in this situation. The West decision has neither been overruled nor questioned in our subsequent cases. It is fully consistent with later developments and has been followed without protest for 24 years. Since we find that the United States acted with the requisite care and prudence in following West, the decision below must be reversed with instructions to enter judgment dismissing the complaint.
So ordered.
Mr. Justice Douglas concurs in the result.
Notes
The land in question originally belonged to the Cherokee Nation, but in 1866, the Cherokees entered a treaty with the United States authorizing the United States to settle friendly Indians in Cherokee territory. See 14 Stat. 799. Pursuant to this treaty, the Osage Indians settled the land in question, and in 1883, the Cherokees conveyed the area to the United States to be held in trust for the
*393
Osage Indians. See
West
v.
Oklahoma Tax Comm’n,
The Act followed the pattern of the General Allotment Act of 1887, 24 Stat. 388, 25 U. S. C. § 331, which empowered the President to allot reservation land to certain Indians, but from which the Osage Indians were omitted.
The Act has been frequently amended. 78 Stat. 1008; 61 Stat. 747 ; 52 Stat. 1034 ; 45 Stat. 1478; 37 Stat. 86.
Originally, the Act provided that the property in question would vest in the Indians in 25 years. See 34 Stat. 544. However, an amendment was passed in 1938 extending the trust period to 1984. See 52 Stat. 1035.
The suit was brought under 28 U. S. C. § 1491, which gives the Court of Claims jurisdiction “to render judgment upon any claim against the United States founded either upon the Constitution, or any Act of Congress, or any regulation of an executive department, or upon any express or implied contract with the United States, or for liquidated or unliquidated damages in cases not sounding in tort.”
Both the United States, as 'defendant below, and Oklahoma, as third-party defendant below, petitioned for certiorari. We granted both petitions, cf. 41 U. S. C. § 114 (b), and consolidated the cases.
Respondents argue before this Court that our recent decision in
McClanahan
v.
Arizona State Tax Comm’n,
The Court of Claims relied in part upon a Technical Advice Memorandum issued by the Internal Revenue Service to the Oklahoma District Director of Internal Revenue on August 15, 1969. The Memorandum announced that, henceforth, Osage trust property would be exempt from federal estate taxation. The court also pointed to Beartrack v. United States, Ct. Cl. No. 281-67, in which the United States settled a suit for refund of federal estate taxes paid on restricted trust properties. It is obvious, however, that Internal Revenue Service decisions as to the scope of its own taxing power have no effect on the taxing power of the States.
As all parties apparently recognize, the scope of the United States’ fiduciary duty in administering the trust property is a question of federal law. Cf.
Clearfield Trust Co.
v.
United States,
