Since Assam updated its National Register of Citizens, other Bharatiya Janata Party-ruled states have threatened to follow suit. Over the past week, the chief ministers of Uttar Pradesh, Uttarakhand and Haryana have said they are open to implementing the exercise.

This should not be a surprise. In the NRC, which aims to sift Indian citizens from so-called illegal immigrants, the BJP has found a perfect template for its exclusionary imagination. Union Home Minister Amit Shah has been promising to expel “infiltrators” (or “termites”, as he has referred to them) from the country for a while now. In the BJP’s communalised vision of the state, such infiltrators are invariably Muslim, while Hindus are natural Indian citizens. The dehumanising language used to describe undocumented migrants also suggests BJP leaders are unmoved by the potential humanitarian crisis – in Assam alone, 19 lakh people left out of the NRC face statelessness and incarceration.

But first, the BJP needs to answer some logistical questions about a nationwide NRC. Who will be counted as an Indian citizen? What does the BJP propose to do with the millions left out of such an NRC and eventually declared foreigners?

In Assam, the exercise to update the NRC stemmed from the anxieties of a border state and from a specific history of migration and colonial resettlement which sharpened the ethnic divide between those defined as indigenous Assamese and those seen as outsiders to the state. The criteria for citizenship was defined by the Assam Accord of 1985 and is tied to the Bangladesh War, which triggered a wave of migration across the border. Anyone who could not prove that they or their ancestors entered the state before midnight on March 24, 1971, or the eve of the Bangladesh War, would be declared a foreigner and deported, the accord said.

In a national landscape, it becomes more complicated. Except Assam, the cut-off date for migrants from Pakistan and former East Pakistan is July 19, 1948. Will millions of people in India now have to prove descent from this population to be considered citizens? Even with a 1971 cut-off date in Assam, it turned out to be a chaotic process, as people scrambled to find proof and were rejected for minor clerical errors in decades-old documents. As two senior Supreme Court lawyers pointed out recently, anyone born in India between 1950 and 1987 is a citizen by birth – a clause overlooked in Assam. Will a nationwide count correct this omission? Besides, if the NRC is implemented statewise, will the modalities to prove citizenship differ from state to state?

The Assam NRC has left all political factions disappointed. Assamese nationalists feel the number of exclusions is too low The subtext to the BJP‘s objections has been communal – too many Muslims included and too many Hindus excluded. Apart from an openly discriminatory criteria for citizenship, however, it may never get the desired result.

Second, in Assam alone, state capacity to deal with the lakhs excluded by the NRC has been severely stretched. Every stage of the process is built for chaos - from the mammoth bureaucratic task of counting citizens, to the business of declaring foreigners in the quasi-judicial foreigners tribunals, to the question of what happens to those stripped of citizenship.

Since there is no repatriation treaty with Bangladesh, this population is effectively stateless. So far, the only option put forward by the government is to lock them up in detention centres. While a new detention centre in Goalpara is to house 3,000 declared foreigners, it may be grossly inadequate for the number finally left stateless. The process has not been cheap either. It took 52,000 government employees and Rs 1,220 crore to compile an NRC that is widely believed to be flawed. The Goalpara detention centre is estimated to cost Rs 46 crore.

Replicated across the country, the NRC become a nightmare of staggering scale - lakhs of government employees, thousands of tribunals, tribunal members and lawyers, millions of stateless people housed in multiplying detention camps, billions of rupees spent on hunting down the elusive infiltrator. Going by logistics alone, a nationwide NRC sounds more like the neurosis of a troubled state than a rational project.