There are rules for everything these days. In fact, most professionals have rules you have to follow in order to work with them. Yet lawyers never seem to make rules for themselves when it comes to clients, payment and acceptable behavior/participation.
This video has more on this topic.
If you run your own law firm you get to make the rules. Period.
The key lies in not only establishing the rules but also in enforcing the rules. Legal marketing requires consistency. Run your law firm how ever you would like just be legal, more and ethical and consistent.