The new ban is the strictest ever in India and includes penalties even for possessing beef. Breaking the law, which languished for five years before getting passed under a conservative ruling Hindu party, brings a fine and up to five years in prison.

Many Mumbai meat sellers are on strike in response, and eateries that feature kabobs and minced-meat delicacies in the Muslim quarter are losing customers. Some have closed. 

If the social agenda of Prime Minister Narendra Modi, takes further hold, the beef ban is likely to spread to other states and add to recent Hindu-oriented policies that have made an impact on school curricula and language requirements. A centuries-old sectarian battle is shifting to new grounds, say many analysts and intellectuals.

Cows are considered sacred by Hindus, who make up more than 80 percent of India's 1.2 billion population. But Muslims and Christians and many of India's tribes and castes are beef eaters. In states like Kerala in the south and West Bengal in the northeast, cattle slaughter is legal and beef is eaten regularly—even by Hindus.

“This is not about protecting cows, it is all about playing politics,” said M. B. Rajesh, a member of parliament from Kerala. “What one should eat or wear are personal choices and they simply cannot be imposed.”

Prime Minister Modi, a professed vegetarian who led his BJP Hindu party to a landslide win in last year's general election, has long spoken against beef exports and has expressed hope for a national ban on cow slaughter. Last spring, many Indians took this as only campaign rhetoric.

But the states of Maharashtra where Mumbai is situated, and Haryana, where beef was recently banned, are ruled by his BJP party.

Ironically perhaps, India is the world's second-largest producer of beef after Brazil. Yet due to religious sentiments and bans in various states, most of India's beef is exported to countries including Vietnam, Malaysia, Indonesia, Bangladesh, Thailand, and Egypt.

Much of the meat now sparking political divisions is not actually from cows. Much of it is from water buffalo, which in Hindu mythology is the “lord of death” and not regarded as holy.

There is no national ban on beef; every state has its own laws on cow slaughter and beef sales. The issue is fraught; in some states, cow slaughter has led to communal clashes and police have at times arrested butchers for violating the law. But even in states with bans, beef is easily found to purchase. In Delhi, for example, where there is a ban, restaurants regularly serve beef. 

The hardest hit group in India are the Muslims who have a corner on the beef business and feel themselves targeted by the ban.

“The ban will render tens of thousands of people jobless,” said Mohammad Ali Qureshi, president of the Mumbai Suburban Beef Dealers Association. “What are we going to do? The [beef] industry doesn't know how to deal with this. We are all worried about future."

Given the sensitivity of cow slaughter, influential Indian Muslims have appealed to the civic nature of their constituency and asked that Muslims avoid cow slaughter on Eid, a Muslim festival.

Resentment surfaced recently in Mumbai after the Vishwa Hindu Parishad, or World Hindu Council, a Hindu nationalist group tied to Modi’s ruling party, allegedly shut down several meat sellers. The VHP has now launched a “save the cow campaign” in Kerala and in a number of other states.