Idaho Code § 39-257
When a person born in Idaho has been legitimated by the subsequent marriage of said person's natural parents and immediately assumes or is assigned a name other than is shown on the recorded birth certificate, the birth certificate of such person may be replaced by a new and conventional certificate (prepared and filed by the state registrar), reflecting the name so assumed or assigned, upon proper application therefor filed by such legitimated person or the parents or one of them, but no one else. Such application shall be in writing and shall be accompanied by a copy of the relevant marriage certificate (if there was one issued and regardless of where it was issued), certified by the issuer or recorder of the same, and, in any event, an affidavit of each of the spouses, factually indicating such parentage, the time and place of the marriage, the identity of the child concerned and the child named in the original birth certificate and giving the assumed or assigned name of the child, which instruments shall be filed of record along with the old birth certificate, but separate from any replacement issued hereunder (which shall be filed separately).
When a person born in Idaho has had said person's natural parentage finally determined by an Idaho court, the court shall require the preparation of a report of paternity on a form prescribed and furnished by the state registrar. The report shall include such facts as necessary to complete the amended birth certificate and be certified by the clerk of the court. If a court of some other state issued a decree or report of paternity, the state registrar may prepare and file a new and conventional birth certificate for that person, reflecting the name(s) of the parent(s) and the child's new name, if applicable, upon application made by that person or either or both of the persons adjudged to be the natural parent(s), or that person's guardian, but no one else. This application shall be accompanied by a certified copy of the court decree in question and an affidavit of one (1) person factually indicating that the decree involves the same person that the original birth certificate involved. These instruments shall be filed of record along with the old birth certificate, but separate from any replacement issued hereunder (which shall be filed separately).
It shall be the duty of each clerk of court in the state of Idaho to file with the state registrar certified copies of each final decree of paternity determination made by that court within fifteen (15) days after each of such decrees becomes final. Such certified copies of such decrees and all other instruments mentioned in this section, except any replacement certificate, are confidential and shall not be revealed to any person other than the registrant, if of age, the parents or the duly appointed legal representative of any of them, or upon court order issued in the interest of justice.
Idaho Code § 39-257