42 U.S.C. 666
I think PastorDon is referring to 42 U.S.C. 666(a)(13)(A).
Section 666. Requirement of statutorily prescribed procedures to improve effectiveness of child support enforcement 
(a) Types of procedures required
      In order to satisfy section 654(20)(A) of this title, each State
    must have in effect laws requiring the use of the following
    procedures, consistent with this section and with regulations of
    the Secretary, to increase the effectiveness of the program which
    the State administers under this part:
(13) Recording of social security numbers in certain family
      matters. - Procedures requiring that the social security number
      of -
          (A) any applicant for a professional license, driver's
        license, occupational license, recreational license, or
        marriage license be recorded on the application;
Y'know, the real problem here is that this is the 42nd Title and has at least 666 Sections.   How many laws do we really need?