The Motor Vehicles Act. 2019 was recently passed by the Indian Parliament but some states like West Bengal have refused to enact the law in their states whereas states like Gujarat have drastically reduced the fines mentioned in the bills.
So I would like to know how much power does an Indian State have when choosing whether or not to implement a Union law? Is what they're doing constitutional? Also if such changes as concerning the Motor Vehicles Act are states' affair then why did the Union pass such a law?
PS: Please provide other examples to support your explanation. Thanks in advance.