Let’s get the boring part out of the way. Take a look over this document…
(It is all about the OBD 1 and how it pertains to the Clean Air Act of 1990.)
OBD II was developed to bring all car manufacturers in line with one another so that it would be more uniform so that consumers could buy a scan tool that would work and that the computer language uniform so there would not be a different scan tool and cable for every manufacturer. Click here for a more in-depth explanation.
There are no laws that say we cannot scan our own vehicles, at least that I can find, however, be very careful when doing so as there are dangers in clearing the computer system that can cause you a very costly repair.
Edgewood Auto Parts #253