India’s southern Kerala State has become the first to legally challenge a new controversial citizenship law in the country that is widely considered anti-Muslim and has triggered nationwide demonstrations.

In a petition filed with the Supreme Court on Tuesday, the administration of the southern state called the Citizenship Amendment Act (CAA) a violation of the secular nature of the Indian constitution and accused the government of dividing the nation along religious lines.

The suit that the Kerala government has filed in the Supreme Court today against the unconstitutional CAA is in line with this fight to save citizens’ rights through constitutional methods, Kerala Chief Minister Pinarayi Vijayan said. Kerala will always remain in the forefront of this fight to protect the Indian constitution and the fundamental rights of its citizens.

He said the state would not implement the law.

The law, backed by Prime Minister Narendra Modi’s Hindu nationalist party, allows granting citizenship to the millions of migrants who came into India - legally or illegally - from Pakistan, Bangladesh, or Afghanistan before December 2014, but not if they are Muslims.

It has sparked nationwide protests. Clashes between the protesters and police have led to nearly two dozen deaths.

Sunny Kappikkad, a prominent Dalit activist, said Sunday that major protests against the CAA had come from the state governments.

Political challenges for Modi over the passage of the new law are mounting, with a number of Indian states saying they will not implement it.

West Bengal Chief Minister Banerjee, a staunch Modi critic, has led several mass rallies in the state against the law. Punjab, Rajasthan, and Madhya Pradesh states, which are governed by the opposition Congress Party, have also announced they will not impose the new law.

The law has also been rejected in the western state of Maharashtra, where Congress is part of a coalition government.

Critics say the law will be used in conjunction with a citizenship list that could require all Indians to produce documents proving their origins, a challenge in a country where many people lack official records, including birth certificates.

Muslims fear the new law may be misused to strip them of their citizenship. The ruling BJP, however, argues the law has nothing to do with the country’s Muslims but aims to help those suffering alleged religious persecution in the neighboring countries.