Indian states continue to oppose a newly amended citizenship law, with Kerala becoming the first to pass a resolution calling for the controversial measure to be repealed.
The Indian government last month put into effect the Citizenship Amendment Act (CAA) that offers citizenship for non-Muslim illegal immigrants from Pakistan, Bangladesh and Afghanistan.
The move prompted widespread protests around the country, with the law criticised for introducing religion as a factor in determining citizenship in a secular country.
There is also a widely held perception that the CAA risks leaving Muslims in India more likely to be declared aliens under a proposed National Register of Citizens (NRC).
India has a federal system of governance and while the Bharatiya Janata Party (BJP) leads the federal government under Prime Minister Narendra Modi, Kerala is governed by the Left Democratic Front, a coalition of left-wing parties.
Last Friday, the state's chief minister, Mr Pinarayi Vijayan, followed up his Dec 31 resolution by asking his counterparts in 11 non-BJP governed states to consider a similar resolution.
Several states governed by non-BJP parties have said they will not implement the CAA and NRC.
The chief ministers of West Bengal and Kerala have also said they will refrain from conducting any activities related to the National Population Register, described as a precursor to the nationwide NRC.
Even Mr Nitish Kumar, the chief minister of Bihar, where the BJP shares power with a regional party led by him, has said he will not let an NRC be held in his state.
However, state-level opposition is limited in its impact as making laws on citizenship is the sole right of the federal Parliament.
Nevertheless, Dr Faizan Mustafa, a constitutional law expert, said state assemblies are still within their rights to pass a resolution expressing their reservations about a law passed by Parliament.
He said: "It is more of a political statement that a state assembly is entitled to make, rather than any constitutional or legal move on citizenship which is the exclusive domain of the Parliament."
Dr Mustafa added that if the 11 other chief ministers also pass a similar resolution against the CAA, then it would create "moral pressure" on the federal government.
"It will highlight the fact that the nation does not speak with one voice when it comes to this law.
"Therefore, the government may be prompted to change its mind even though they have said they won't concede an inch."
While the federal government has the upper hand in legislating on citizenship, it requires state cooperation in implementing the new Act as the logistical support to carry out tasks, such as background checks of applicants, has to be provided for by the local state government.
Ms Arati Jerath, a Delhi-based senior political commentator, told The Straits Times: "So, unless the state governments cooperate with the federal government, it is going to be very difficult for the latter to implement the amended citizenship law or even the NRC, if and when they decide to do it."
If the states defy the federal government, it could have very damaging consequences for India's federal polity, she said. This includes the possibility of rebellious state governments being dismissed by the federal government.
"One is potentially looking at a very serious constitutional crisis if the states choose to go ahead with their threatened revolt on this issue. And this is a real risk because both sides have been very recalcitrant on their respective positions," she added.
The new law has also been challenged by a wide range of litigants in the Supreme Court, which will hear the case on Jan 22.