Question: Yesterday Indian parliament passed citizenship amendment bill which seeks to provide citizenship to religious minorities which have to come to India before Dec 2014 as a refugee due to their persecution in Pakistan, Bangladesh and Afghanistan.

I know it can be challenged in Supreme Court if the President of India signs it which he is most likely to do.

Today Kerala Chief Minister said that he would not allow it to be implemented in his state.

So does a state in India has power to stop implementation of a bill unilaterally?

Answer: 
It is not clear what Vijayan, Banerjee and Singh intend to do to "not implement" the law. One part of [the bill](http://prsindia.org/sites/default/files/bill_files/Citizenship%202019%20Bill%20Text.pdf) adds a paragraph

> 
> 6B. (1) The Central Government *or an authority specified by it* in
>  this behalf may... grant a certificate of registration
> 
> 
> 

These states may decide to not cooperate. This would be analogous to US jurisdictions refusing to cooperate with federal authorities attempting to enforce immigration laws. However, the Bureau of Immigration (analogous to US ICE) may have sufficient resources to enforce the law without any state aid.
The other possibility (suggested by Banerjee's statement that W. Bengal will not allow the government to "throw out a legal citizen of the country or turn the person into a refugee")
is that this relates to the theory that the law will be used to expel Muslim refugees. A state could not directly prevent the central government from carrying out such a plan, but it could refuse to cooperate. Since as I understand it public order, police, and prisons are on the [State List](https://en.wikipedia.org/wiki/State_List) under Art. 246 of the Constitution, and the [Union list](https://en.wikipedia.org/wiki/Union_List) do not seem to provide for the kind of sweeps that have been suggested could result from the law (unless the military executes the plan). There is no question that citizenship laws are on the Union List.
India is a quasi-federation
---------------------------

Powers are split between the state and national government as detailed in the [constitution](https://en.wikipedia.org/wiki/Constitution_of_India#Constitution_and_government). India is a halfway point between full federations (e.g. USA, Australia) and unitary nations (e.g. France, Austria) - it still has sovereign states like a federation but the national government has much more power to intervene.

Notwithstanding, citizenship is solely the province of the national government - Indian states have **no** power over it.