Why some people oppose NRC?

* The NRC Bill aims to create a comprehensive list of all legal citizens of India.    * The NRC was first implemented in the state of Assam in 1951, and it was updated in 2019. * The government has stated its intention to implement the NRC nationwide, but the details of how this will be done are still unclear.    * The NRC Bill is a controversial issue, with some people supporting it and others opposing it. What could be a reason to oppose this step?