concurring.
I fully agree that the extent of the 1866 federal grant to which Mrs. Hughes traces her ownership was originally measurable by federal common law, and that under the applicable federal rule her predecessor in title acquired the right to all accretions gradually built up by the sea. For me, however, that does not end the matter. For the Supreme Court of Washington decided in 1966, in the case now before us, that Washington terminated the *295right to oceanfront accretions when it became a State in 1889. The State concedes that the federal grant in question conferred such a right prior to 1889. But the State purports to have reserved all post-1889 accretions for the public domain. Mrs. Hughes is entitled to the beach she claims in this case only if the State failed in its effort to abolish all private rights to seashore accretions.
Surely it must be conceded as a general proposition that the law of real property is, under our Constitution, left to the individual States to develop and administer. And surely Washington or any other State is free to make changes, either legislative or judicial, in its general rules of real property law, including the rules governing the property rights of riparian owners. Nor are riparian owners who derive their title from the United States somehow immune from the changing impact of these general state rules. Joy v. St. Louis, 201 U. S. 332, 342. For if they were, then the property law of a State like Washington, carved entirely out of federal territory, would be forever frozen into the mold it occupied on the date of the State’s admission to the Union. It follows that Mrs. Hughes cannot claim immunity from changes in the property law of Washington simply because her title derives from a federal grant. Like any other property owner, however, Mrs. Hughes may insist, quite apart from the federal origin of her title, that the State not take her land without just compensation. Chicago, B. & Q. R. Co. v. Chicago, 166 U. S. 226, 236-241.
Accordingly, if Article 17 of the Washington Constitution had unambiguously provided, in 1889, that all accretions along the Washington coast from that day forward would belong to the State rather than to private riparian owners, this case would present two questions not discussed by the Court, both of which I think exceedingly difficult. First: Does such a prospective change in state *296property law constitute a compensable taking? Second: If so, does the constitutional right to compensation run with the land, so as to give not only the 1889 owner, but also his successors — including. Mrs. Hughes — a valid claim against the State?
The fact, however, is that Article 17 contained no such unambiguous provision. In that Article, the State simply asserted its ownership of “the beds and shores of all navigable waters in the state up to and including the line of ordinary high tide, in waters where the tide ebbs and flows, and up to and including the line of ordinary high water within the banks of all navigable rivers and lakes.” In the present case the Supreme Court of Washington held that, by this 1889 language, “[l]ittoral rights of upland owners were terminated.” 67 Wash. 2d 799, 816, 410 P. 2d 20, 29. Such a conclusion by the State's highest court on a question of state law would ordinarily bind this Court, but here the state and federal questions are inextricably intertwined. For if it cannot reasonably be said that the littoral rights of upland owners were terminated in 1889, then the effect of the decision now before us is to take from these owners, without compensation, land deposited by the Pacific Ocean from 1889 to 1966.
We cannot resolve the federal question whether there has been such a taking without first making a determination of our own as to who owned the seashore accretions between 1889 and 1966. To the extent that the decision of the Supreme Court of Washington on that issue arguably conforms to reasonable expectations, we must of course accept it as conclusive. But to the extent that it constitutes a sudden change in state law, unpredictable in terms of the relevant precedents, no such deference would be appropriate. For a State cannot be permitted to defeat the constitutional prohibition against taking property without due process of law by the simple *297device of asserting retroactively that the property it has taken never existed at all. Whether the decision here worked an unpredictable change in state law thus inevitably presents a federal question for the determination of this Court. See Demorest v. City Bank Co., 321 U. S. 36, 42-43. Cf. Indiana ex rel. Anderson v. Brand, 303 U. S. 95. The Washington court insisted that its decision was “not startling.” 67 Wash. 2d 799, 814, 410 P. 2d 20, 28. What is at issue here is the accuracy of that characterization.
The state court rested its result upon Eisenbach v. Hatfield, 2 Wash. 236, 26 P. 539, but that decision involved only the relative rights of the State and the upland owner in the tidelands themselves. The Eisen-bach court declined to resolve the accretions question presented here. This question was resolved in 1946, in Ghione v. State, 26 Wash. 2d 635, 175 P. 2d 955. There the State asserted, as it does here, that Article 17 operated to deprive private riparian owners of post-1889 accretions. The Washington Supreme Court rejected that assertion in Ghione and held that, after 1889 as before, title to gradual accretions under Washington law vested in the owner of the adjoining land. In the present case, 20 years after its Ghione decision, the Washington Supreme Court reached a different conclusion. The state court in this case sought to distinguish Ghione: The water there involved was part of a river. But the Ghione court had emphatically stated that the same “rule of accretion . . . applies to both tidewaters and fresh waters.” 26 Wash. 2d 635, 645, 175 P. 2d 955, 961. I can only conclude, as did the dissenting judge below, that the state court’s most recent construction of Article 17 effected an unforeseeable change in Washington property law as expounded by the State Supreme Court.
There can be little doubt about the impact of that change upon Mrs. Hughes: The beach she had every *298reason to regard as hers was declared by the state court to be in the public domain. Of course the court did not conceive of this action as a taking. As is so often the case when a State exercises its power to make law, or to regulate, or to pursue a public project, pre-existing property interests were impaired here without any calculated decision to deprive anyone of what he once owned. But the Constitution measures a taking of property not by what a State says, or by what it intends, but by what it does. Although the State in this case made no attempt to take the accreted lands by eminent domain, it achieved the same result by effecting a retroactive transformation of private into public property — without paying for the privilege of doing so. Because the Due Process Clause of the Fourteenth Amendment forbids such confiscation by a State, no less through its courts than through its legislature, and no less when a taking is unintended than when it is deliberate, I join in reversing the judgment.