FACAAB Chairman Hiren Gohain, a noted litterateur and educationist, said the "Our lawyers are studying the Act and will file a foolproof petition in coming days."
On the violent protest against the Act, FACAAB Convenor and senior journalist Manjit Mahanta claimed, "We suspect that the government is behind this. They are trying to defame and derail the spontaneous public agitation. An attempt is also made to give it a communal colour."
At a separate media interaction, ANS General Secretary Paresh Malakar said the organisation will move the Supreme Court against the Act.
Along with the legal battle, democratic protests will continue and people should be ready to dethrone the "anti- Assam" BJP from power in the next opportunity, Malakar said.
Assembly election in the state is due in 2021.
Both the organisations condemned the arrest of Krishak Mukti Sangram Samiti (KMSS) Adviser Akhil Gogoi and others and demanded their immediate release.
Gogoi was arrested on Thursday as a preventive measure in view of the deteriorating law and order situation in the state and his colleagues were taken into custody the next day.
Assam is witnessing one of the worst violent protests in its history with three rail stations, a post office, a bank, a bus terminus, shops, dozens of vehicles and many other public properties being set ablaze or ransacked.
After the Rajya Sabha passed the Citizenship (Amendment) Bill on Wednesday night, the state erupted in protests, in which agitators engaged in pitched battles with the police in a number of cities and towns, forcing the administration to impose curfew.