It all Starts Here:
TITLE 49 Sec. 31102. - Grants to States
SUBTITLE VI - MOTOR VEHICLE AND DRIVER PROGRAMS
PART B - COMMERCIAL
CHAPTER 311 - COMMERCIAL MOTOR VEHICLE SAFETY
SUBCHAPTER I - GENERAL AUTHORITY AND STATE GRANTS
- (b) State Plan Procedures and Contents. -
(1)The Secretary shall prescribe procedures for a State to submit a plan . . . The Secretary shall approve the plan . . and the plan -
(B)
designates the State motor vehicle safety agency responsible for administering the plan throughout the State;
(C)
contains satisfactory assurances the agency has or will have the legal authority, resources, and qualified personnel necessary to enforce the regulations, standards, and orders;
That is just for context, you really need to read the whole section to understand the regulatory scheme