In the adjustment of all railroad land grants, whether made directly to any railroad company or to any State for railroad purposes, if any of the lands granted be found in the possession of an actual settler whose entry or filing has been allowed under the preemption or homestead laws of the United States subsequent to the time at which, by the decision of the land office, the right of said road was declared to have attached to such lands, the grantees, upon a proper relinquishment of the lands so entered or filed for, shall be entitled to select an equal quantity of other lands in lieu thereof from any of the public lands not mineral and within the limits of the grant not otherwise appropriated at the date of selection, to which they shall receive title the same as though originally granted. And any such entries or filings thus relieved from conflict may be perfected into complete title as if such lands had not been granted: Provided, That nothing herein contained shall in any manner be so construed as to enlarge or extend any grant to any such railroad or to extend to lands reserved in any land grant made for railroad purposes: And provided further, That this section shall not be construed so as in any manner to confirm or legalize any decision or ruling of the Interior Department under which lands have been certified to any railroad company when such lands have been entered by a preemption or homestead settler after the location of the line of the road and prior to the notice to the local land office of the withdrawal of such lands from market.