Here's my thought. In Louisiana when the DOT book came out I believe there was Fed pressure to all states to incorporate those laws and become more standard. Louisiana incorporated into law the complete book. However they have changed many of the requirements of the book many times. However if the DOT book is considered federal law the states can change the requirements but can't make them less lenient. Also in my view if a state incorporated the fed requirements into law they implicity incorporated the guidance book also. You can't have a fed law and a state law using the exact same words meaning two different things and the feds have provided interpretation for many requirements in the guidance book.