MR. JUSTICE STONE delivered the opinion of the Court.
The relators, petitioners here, filed their petition in the Supreme Court of the District of Columbia for a writ of mandamus to compel the Secretary of War and the Chief of Engineers to authorize the construction of a wharf in the Potomac River within the District of Columbia adjacent to their land on the Virginia shore, the construction being forbidden by § 10 of the Act of March 3, 1899, c. 425, 30 Stat. 1121, 1151, 33 U.S.C., § 403, "except on plans recommended by the Chief of Engineers and authorized by the Secretary of War." The judgment of the Supreme Court denying the writ was affirmed by the District Court of Appeals. 61 App.D.C. 360; 63 F.2d 137. This Court granted certiorari. 288 U.S. 598.
Petitioners claim title through a grant to their predecessors in interest of a plot of upland lying in the
Petitioners have entered into a contract for the sale of their lands, conditioned upon securing permission to build the wharf, which is to be built and used by the purchaser in connection with a plant to be established on the upland for the storage of gasoline. It is stipulated on the record that the proposed wharf, which is to be constructed in conformity to plans approved by the Chief of Engineers,
"The citizens of each state respectively shall have full property in the shores of Patowmack River adjoining their lands, with all emoluments and advantages thereunto belonging, and the privilege of making and carrying out wharfs and other improvements, so as not to obstruct or injure the navigation of the river; . . ."
They insist that as the proposed wharf will not interfere with navigation and as plans for its construction have been approved by the Chief of Engineers, it is the legal duty of the Secretary of War, under § 10 of the Rivers and Harbors Appropriation Act of March 3, 1899, to grant the desired permit. It is conceded by the government that the only basis for the Secretary's refusal to authorize the construction of the wharf is that it would be inimical to the establishment of the proposed George Washington Memorial Parkway authorized by Act of Congress of May 29, 1930, c. 354, 46 Stat. 482.
By this legislation Congress appropriated $7,500,000 for the construction of a parkway a part of which is to extend along the Virginia shore of the Potomac River from Mount Vernon to a point above the Great Falls.
Pending this suit, but before its trial, the Park and Planning Commission, by resolutions of September 24-26, 1931, declared that certain lands of the United States, described by metes and bounds, running along the high water line of 1863 on the Virginia side of the river, as established by United States Coast Survey, and extending to the center line of the channel of the river, are necessary for the development and protection of the Parkway. By further resolution, the Commission declared that it took complete and exclusive possession of these lands, which include the river bed where it is proposed to build the wharf and the upland claimed by petitioners by accretion. It directed that copies of the resolutions be posted on each parcel, which was done before the hearing in this suit. A description of each was also sent to the Attorney General for the purpose of having suits filed under the Act of April 27, 1912, c. 96, 37 Stat. 93, which authorizes suits by the Attorney General to quiet title to lands adversely held or claimed lying under and adjacent to the Potomac
It is apparent that petitioners are entitled to the relief prayed only if several doubtful questions are resolved in their favor. They are (1) whether a mandatory duty is imposed upon the Secretary of War by § 10 of the Rivers and Harbors Appropriation Act to authorize the construction of the proposed wharf if he is satisfied that it will not interfere with navigation; (2) whether in fact petitioners have title, by accretion, to the upland adjacent to the river at the point where it is proposed to build the wharf, and thus have the status of riparian owners; (3) whether even as riparian owners of land lying within Virginia, petitioners, in the absence of a legislative grant either by Maryland before the cession or by the United States after it, have a common law right to build a wharf on the adjacent lands of the United States lying in the bed of the river, see Casey's Lessee v. Inloes, 1 Gill 430; Browne v. Kennedy, 5 Harris & J. 195; Giraud's Lessee v. Hughes, 1 Gill & Johns. 249, 265; Wilson's Lessee v. Inloes, 11 Gill & Johns. 351; Hammond's Lessee v. Inloes, 4 Md. 138; Horner v. Pleasants, 66 Md. 475; 7 Atl. 691; Attorney General v. Hudson County Water Co., 76 N.J. Eq. 543; 76 Atl. 560, or if not (4) whether their predecessors in title acquired such a right under Paragraph Seventh of the Maryland-Virginia Compact, Georgetown v. Alexandria Canal Co., 12 Pet. 91; Potomac Steamboat Co. v. Upper Potomac Steamboat Co., 109 U.S. 672, 675; (5) whether, if such a right were derived from the Compact, it was not lost before its exercise by the union in the single ownership of the United States of the land under the river, and on both sides of it, which resulted from the cession by Maryland and Virginia of the area originally embraced in the District of Columbia and continued until the retrocession
The Government contends that in view of the nature of these questions the case is not an appropriate one for mandamus, since ordinarily mandamus against a public officer will not lie unless the right of the petitioner and the duty of the officer, performance of which is to be commanded, are both clear. See McLennan v. Wilbur, 283 U.S. 414, 419, 420; Interstate Commerce Commission v. New York, New Haven & Hartford R. Co., 287 U.S. 178; Redfield v. Windom, 137 U.S. 636; Bayard v. White, 127 U.S. 246. It is insisted that both the petitioners' riparian ownership and the right to build the wharf which they claim to have derived from it, are doubtful; and in any event that the duty of the Secretary under the statute
But we find it unnecessary, in the circumstances of this case, to say what effect should be given to these objections alone, whether considered each separately or together. Although the remedy by mandamus is at law, its allowance is controlled by equitable principles, see Duncan Townsite Co. v. Lane, 245 U.S. 308, 311; Arant v. Lane, 249 U.S. 367, 371; Redfield v. Windom, supra, 644; cf. Turner v. Fisher, 222 U.S. 204; Ex parte Skinner & Eddy Corp., 265 U.S. 86, 95; People ex rel. Wood v. Assessors, 137 N.Y. 201; 33 N.E. 145; Matter of Lindgren, 232 N.Y. 59; 133 N.E. 353; McCarthy v. Street Comm'rs, 188 Mass. 338; 74 N.E. 659; People ex rel. Stettauer v. Olsen, 215 Ill. 620; 74 N.E. 785, and it may be refused for reasons comparable to those which would lead a court of equity, in the exercise of a sound discretion, to withhold its protection of an undoubted legal right. For such reasons we think the relief sought by
The court, in its discretion, may refuse mandamus to compel the doing of an idle act, Turner v. Fisher, supra, 209; Wilson v. Blake, 169 Cal. 449; 147 Pac. 129; or to give a remedy which would work a public injury or embarrassment, (see Duncan Townsite Co. v. Lane, supra; Arant v. Lane, supra; Effingham, Maynard & Co. v. Hamilton, 68 Miss. 523; 10 So. 39; cf. Matter of Lindgren, supra, 66; McCarthy v. Street Comm'rs, supra) just as in its sound discretion a court of equity may refuse to enforce or protect legal rights, the exercise of which may be prejudicial to the public interest. See Seaboard Air Line Ry. Co. v. Atlanta B. & C.R. Co., 35 F.2d 609;