I highly recommend that you disregard everything that anyone (including myself) has to say here and investigate it yourself with your local DMV/DOT. In my state, there are different rules if you are engaged in intrastate or interstate commerce. It is my undertanding that I am not subject to the CGVWR of 10.001K unless I cross state lines, but instead subject to them if I'm 18,001 pounds combined, so with my 3K gross trailer I'm not. But yes, generally it's the rating of the rig that triggers things, not whether you are actually over it at the time.
This has come up time and time again here and there is little concensus and a lot of misinformation. It's really best to check how things are in your state. There are also some rigs that automatically trigger the regulations, regardless of weight rating. There are also some exemptions. The key to it all...the applicablility...lies in the defintions and how they are interpreted and enforced.