Citizens across India have turned out in recent weeks to protest a controversial piece of legislation known as the Citizenship Amendment Act (CAA). The CAA became law on Dec. 11, after the upper house of India’s Parliament passed the measure and the country’s president gave it his assent.

India’s government — headed by the Hindu-nationalist Bharatiya Janata Party (BJP) — holds that the CAA will make it easier for people from “persecuted minorities” in the country illegally to obtain Indian citizenship. It argues that the CAA is an important improvement to the Citizenship Act of 1955, which left people in the country illegally without any avenues to become citizens. Consequently, millions residing within India’s borders have long been vulnerable to detention and deportation.

So why are people protesting? Here’s what you need to know:

1. Motivations to join the protests differ greatly

Mass protests — like those underway in India — often appear to be driven by a shared set of concerns. But a well-established literature in political science and sociology has shown that individuals come to participate in demonstrations for many different reasons. These motivations can be related to widely held grievances, but resources and opportunities to engage in protest also matter.

Moreover, coalitions that give rise to mass demonstrations often change across space and time. For instance, comparative findings from the protests in Egypt and Tunisia during the Arab Spring reveal that although experts described those revolutions as “youth rebellions,” the class composition of the young people who participated was different across the two cases.

2. Indians oppose the CAA for various reasons

These insights are helpful to understand the anti-CAA turnout in India, where protesters appear to have several motivations. The earliest demonstrations broke out in the northeastern state of Assam on Dec. 4. In this case, fears over fast-track citizenship for Bangladeshi Hindus — whom many perceive as outsiders — culminated in mass protests.

A lengthy history of “sons of the soil” grievances against individuals from Bangladesh — who have illegally come to live in this part of India in large numbers — provides crucial background for Assam’s protests. These grievances have fueled clashes between incoming migrants and native populations, and in the past gave rise to a brutal civil war that was at its peak until 2011. The conflict started with demonstrations — led by the All Assam Students’ Union (AASU) — against the influx of Muslim immigrants from Bangladesh and resulted in the formation of the United Liberation Front of Assam (ULFA) rebel group. But Assamese today also oppose providing citizenship to Bangladeshi Hindus.

Elsewhere in India, different concerns appear to be driving the anti-CAA demonstrations. In cities like New Delhi, Hyderabad, Aligarh and Lucknow, protesters have turned out to object to the “anti-Muslim” nature of the legislation. While the CAA makes it possible for Hindus, Sikhs, Christians, Buddhists, Jains and Parsees who came to India from Afghanistan, Pakistan and Bangladesh before Dec. 31, 2014, to obtain Indian citizenship, it excludes Muslims from taking this route. The government’s position is that Muslims cannot be a “persecuted minority” since they constitute the majority in these three countries.

Students have been at the forefront of the urban protests, along with academics, authors and activists. Muslims, who reside in many Indian cities in large numbers, have also joined in. These demonstrators argue that by excluding Muslims, the CAA violates the country’s secular principles — and risks turning India into a majoritarian state. Many also cite concerns that the country’s Muslim community already experiences political and socioeconomic marginalization.

The police have cracked down on demonstrators — over 80 students from the Jamia Millia Islamia University had to seek treatment at a major New Delhi hospital two weeks ago, and 25 protesters have lost their lives thus far.

Meanwhile, the government has suspended mobile communications — and the Internet — in various parts of the country. Prime Minister Narendra Modi has condemned the protests and tweeted that “no Indian has anything to worry regarding this Act.” Home Minister Amit Shah added that “Muslims have no need to fear or worry.” But such declarations will probably mean little to those who are concerned that the BJP is trying to create a “Hindu nation” in India, a country that is 80 percent Hindu.

3. Large cities offer a springboard for organizing protests

The urban nature of India’s current demonstrations is consistent with patterns of collective action observed during the Arab Spring, and with emerging insights about the “revolutionary advantages of cities.” This research suggests that the concentration of large numbers of people — coupled with the presence of interconnected urban groups — make cities particularly potent sites for mobilizing protests.

An extensive literature on Hindu-Muslim riots has also highlighted the city-centric nature of such violence in India. Many scholars have attributed communal riots to the dense networks that link politicians, activists and criminals in urban spaces.

Of course, India is home to some of the most populated cities on the planet, and rural-to-urban migration in the country seems likely to increase over the next decade. This suggests that urban hubs will continue to serve as sites for collective action.

4. India has a long history of public protests

Protest activity in modern India dates back to agitations against British colonial practices. India is also famous for nonviolent resistance campaigns that took place during the freedom struggle.

After independence in 1947, Indians have continued to protest a range of issues. These include farmers’ demonstrations against the government, and protests against discrimination and oppression of India’s Dalits — the group formerly known as “untouchables.” Recently, the country has also witnessed a surge in mass agitations against sexual violence. Thus, the broader background of contentious politics in India offers another way to understand the current protests. Indians have a history of demonstrating against perceived injustices, and the CAA is the latest development that many believe is unfair.

Some observers have drawn parallels between the present demonstrations and those in the 1970s — also led by students — over discontent with the government of Prime Minister Indira Gandhi. Those protests revitalized Indian democracy against a rising authoritarianism. Demonstrators undoubtedly hope that the present protests will have the same result.

Aditi Malik (@aditimalik_) is an assistant professor of political science at the College of the Holy Cross. She studies political violence, political parties, ethnic politics and social movements in South Asia and sub-Saharan Africa.

Shivaji Mukherjee (@ShivajiMukherj3) is an assistant professor of political science at the University of Toronto. He studies civil war, political violence and colonial origins of the Maoist insurgency in India.

Ajay Verghese (@ajayverghese) is an assistant professor of political science at the University of California at Riverside and the author of “The Colonial Origins of Ethnic Violence in India” (Stanford University Press, 2016).