Hello,

You cannot become a professor after merely completing graduation in law. There's no direct route to become professor, because first of all when you join any college after completing your master's degree and qualifying NET you become assistant professor,then associate professor and eventually professor,it takes long time to go through these roles.

The first thing you should do if you've completed your graduation in law is to persue postgraduation further and qualify NET/SET,whatever you prefer SET is conducted on a state level and NET is conducted on a national level.