The regulation pertaining to trailers of 10,001 lbs more more has not really changed since CDL became required.



There is a farm exemption, but then you have the burden of proving that the vehicle is actually being used for farm use.

http://www.fmcsa.dot.gov/about/news/news-releases/2011/Transportation-Reinforces-Committment.aspx

The states were mandated to create the CDL system. Certain exceptions of state laws are grandfathered. For instance Texas is grand fathered with its 150 mile radious and its 12 hour driving time. However, once a state line is crossed. the driver is regulated by federal regulations for 7 days.