SAN JOSE, Calif. — For several years now, America’s malls have seen a growing number of incidents around Christmas starring young people behaving badly, often near food courts or theaters, sometimes featuring items like soft drinks thrown at security officers, and usually resulting in fist fights and general mayhem.

Malls, in response, are stepping up their security game, increasing staffing for the day after Christmas, when teenagers have run amok in selected properties across the nation. But some operators are also instituting curfews or total bans on unaccompanied minors at certain times, prompting outrage not only from the young shoppers and their parents but from civil-rights activists who say such bans are unfair and illegal.

In the latest example, the Arden Fair mall in Sacramento’s decision to ban teens on Dec. 26 drew strong criticism from the American Civil Liberties Union, which claims such a move is discriminatory and violates California law.

“It’s illegal,” said Michael Risher, a senior staff attorney for the ACLU in San Francisco. “California for decades has had the Unruh Civil Rights Act which prohibits any business from arbitrary discrimination against people based on sex, race, religion and sexual orientation as well as other categories, including minors. The law says you must treat people as individuals, not as a class, so if you have individuals causing problems at a mall, of course they can take action against them.

Risher said a similar ban at a Fresno mall in 2007 was reversed after the ACLU, along with the city of Fresno’s attorney, wrote letters to complain.

“The California Supreme Court has said that while some kids may behave that way, you can’t ban all children” from a business, said Risher, adding that “I can’t imagine that more than a tiny percentage of minors are creating problems in these malls.”

Risher was referring to a 1982 decision against a Los Angeles County landlord who sought to prevent families with children from living in his building. The justices wrote that a property owner may not ban “an individual who has committed no such misconduct” simply because he or she “falls within a class of persons whom the owner believes is more likely to engage in misconduct than some other group.”

But officials at Arden Fair disagree, along with security staff at the estimated 100 other properties that have instituted periodic bans on unaccompanied teenagers.

In an interview Tuesday with The Sacramento Bee, a spokeswoman for Arden Fair defended the new policy, which mall officials describe as a pre-emptive measure designed to ensure the safety of everyone at a mall that in recent years has experienced brawls after Christmas. This season, guards and Sacramento police officers were staged at mall entrances, enforcing a blanket ban on minors not accompanied by a parent or guardian.

Other Northern California malls say they’ve not seen similar problems.

“We have no bans at either Westfield Valley Fair or Westfield Oakridge,” said spokeswoman Caran Fisher. “The holidays are a high-traffic time for families and teens and I can tell you that we did increase our security and traffic control this year to ensure the safety of everyone. Teens are a big part of our customer base and we want to make sure everyone is safe and happy.”

Stephanie Cegielski, vice president of public relations for the International Council of Shopping Centers, said about 100 malls in the United States have reportedly used curfews or bans periodically throughout the year. That’s a relatively small number, given the trade group representing owners of malls and shopping centers has 53,000 members in the United States. Still, she said the number of holiday incidents appears to be on the rise, with a disturbing number of mall fights around the country this holiday season.

This year, the day after Christmas “saw a series of fights that broke out, mostly among young people. Some of this comes from the long holiday weekend and teenagers maybe being bored and then going to the mall to cause some mayhem.”

Cegielski said her group has not heard of other malls being singled out by civil-rights groups as the Sacramento mall has experienced. “I think property owners are concerned,” she said, “and they’re looking at the day after Christmas and they’re putting these bans into place as a means of crowd control. They just want to make the malls safer for everyone.”

Security officials are increasingly concerned that social-media tools like Facebook and Twitter are being used by teens to coordinate meetups at malls that lead to gang fights and other problems. Activists are worried that security guards may be using racial profiling in enforcing the ban on minors, singling out young blacks, for example, when they decide who can come inside and who can’t.

It’s not clear whether the ACLU will go after Arden Fair or any other mall implementing bans.

“We have a lot on our plate right now and we’ll have to monitor and see what happens,” said Risher. “But unless these fights become such a pervasive problem, and you can say that most youths are coming to malls to make trouble, then you can’t ban all teenagers from the property. Bring in more security if this is truly a problem and not just an exaggerated fear.”