"Of course, when we speak of the conclusive presumptions attending a patent for lands, we assume that it was issued in a case where the department had jurisdiction to act and execute it; that is to say, in a case where the lands belonged to the United States, and provision had been made by law for their sale. If they never were public property, or had previously been disposed of, or if Congress had made no provision for their sale, or had reserved them, the department would have no jurisdiction to transfer them, and its attempted conveyance of them would be inoperative and void, no matter with what seeming regularity the forms of law may have been observed. The action of the department would, in that event, be like that of any other special tribunal not having jurisdiction of a case which it had assumed to decide. Matters of this kind, disclosing a want of jurisdiction, may be considered by a court of law. In such cases the objection to a patent reaches beyond the action of a special tribunal, and goes to the existence of a subject upon which it was competent to act.

"The general doctrine declared may be stated in a different form, thus: a patent, in a court of law, is conclusive as to all matters properly determinable by the Land Department, when its action is within the scope of its authority; that is, when it has jurisdiction under the law to convey the land. In that court the patent is unassailable for mere errors of judgment. Indeed the doctrine as to the regularity and validity of its acts, where it has jurisdiction, goes so far that if in any circumstances under existing law a patent would be held valid, it will be presumed that such circumstances existed.

"On the other hand, a patent may be collaterally impeached in any action, and its operation as a conveyance defeated, by showing that the department had no jurisdiction to dispose of the lands; that is, that the law did not provide for selling them, or that they had been preserved from sale or dedicated to special purposes, or had been previously transferred to others. In establishing any of these particulars, the judgment of the department, upon matters properly before it, is not assailed nor is the regularity of its proceedings called into question; but its authority to act at all is denied and shown never to have existed."

In a series of cases, the court has given to customs officers final and conclusive authority in the matter of appraisement and classification of imports.

In Hilton v. Merritt10 it was held that Congress having by statute made the appraisers' judgment final and conclusive, an appeal therefrom might not be made to the judiciary, the court saying: "We are of opinion . . . that the valuation made by the customs officers was not open to question in an action at law, as long as the officers acted without fraud and within the power conferred on them by the statute. The evidence offered by the plaintiffs and ruled out by the court tended only to show carelessness or irregularity in the discharge of their duties by the customs officers, but not that they were assuming powers not conferred by the statute."

In Buttfield v. Stranahan11 the court held conclusive the judgment of the customs officers with reference to the fact whether or not a given importation of tea was of a grade that, under law, entitled it to entrance into the country.