In order to promote the highest use of the public lands pending its final disposal, the Secretary of the Interior is authorized, in his discretion, by order to establish grazing districts or additions thereto and/or to modify the boundaries thereof, of vacant, unappropriated, and unreserved lands from any part of the public domain of the United States (exclusive of Alaska), which are not in national forests, national parks and monuments, Indian reservations, revested Oregon and California Railroad grant lands, or revested Coos Bay Wagon Road grant lands, and which in his opinion are chiefly valuable for grazing and raising forage crops: Provided, That no lands withdrawn or reserved for any other purpose shall be included in any such district except with the approval of the head of the department having jurisdiction thereof. Nothing in this subchapter shall be construed in any way to diminish, restrict, or impair any right which has been heretofore or may be hereafter initiated under existing law validly affecting the public lands, and which is maintained pursuant to such law except as otherwise expressly provided in this subchapter nor to affect any land heretofore or hereafter surveyed which, except for the provisions of this subchapter, would be a part of any grant to any State, nor as limiting or restricting the power or authority of any State as to matters within its jurisdiction. Whenever any grazing district is established pursuant to this subchapter, the Secretary shall grant to owners of land adjacent to such district, upon application of any such owner, such rights-of-way over the lands included in such district for stock-driving purposes as may be necessary for the convenient access by any such owner to marketing facilities or to lands not within such district owned by such person or upon which such person has stock-grazing rights. Neither this subchapter nor the Act of December 29, 1916 (39 Stat. 862; U.S.C., title 43, secs. 291 and following), commonly known as the ''Stock Raising Homestead Act'', shall be construed as limiting the authority or policy of Congress or the President to include in national forests public lands of the character described in section 471 ^[1] of title 16, for the purposes set forth in section 475 of title 16, or such other purposes as Congress may specify. Before grazing districts are created in any State as herein provided, a hearing shall be held in the State, after public notice thereof shall have been given, at such location convenient for the attendance of State officials, and the settlers, residents, and livestock owners of the vicinity, as may be determined by the Secretary of the Interior. No such district shall be established until the expiration of ninety days after such notice shall have been given, nor until twenty days after such hearing shall be held: Provided, however, That the publication of such notice shall have the effect of withdrawing all public lands within the exterior boundary of such proposed grazing districts from all forms of entry of settlement. Nothing in this subchapter shall be construed as in any way altering or restricting the right to hunt or fish within a grazing district in accordance with the laws of the United States or of any State, or as vesting in any permittee any right whatsoever to interfere with hunting or fishing within a grazing district.