Calcutta University is far better than North Bengal University for studying law. 

• CU has more national recognition as compared to North Bengal University.
• The exposure you will get at CU is unparalleled.
• CU is an older university compared to North Bengal University.

Although you can excel in your academics from any university, choosing a better one will provide you with more exposure. So, if you are interested in pursuing a degree in Law, I will suggest that you choose CU.