I hate to be a devil's advocate here, because in principle, I completely agree with you. The law shouldn't be copyrighted.
But in my career, environmental engineering, we deal with a lot of EPA regulations which have adopted a standard developed by ASTM. Since the standards were developed by a private company, they are copyrighted, and my company has to pay that company in order to keep up with the law. This is bad.
But the alternative to adopting standards developed by a private company is the government developing them itself, and as far as I can tell, this will cost just as much money to do as it would cost the private company. The issue that I see here is that now, everyone is paying for that standard to be developed, even though the vast majority of the population will never need to reference those standards.
Yes, I honestly believe that everyone should be allowed to access the law. But since most people wouldn't need to, or even want to, access those sector-specific copyrighted laws, isn't it more fair to have only the professionals in that sector pay for their development?