A public falling-out between two prominent animal-rights activists has prompted a restraining order and an arrest, casting light on the volatile mix of personalities that may fuel extreme elements of the animal-rights movement.

Steven Best, an outspoken advocate of animal rights and philosophy professor at the University of Texas at El Paso, obtained a restraining order on 15 October against fellow activist Camille Marino after she allegedly stalked Best and threatened violence against him. Marino was arrested at her home in Wildwood, Florida, on 19 October for violating the injunction. According to Marino’s website, she had e-mailed Best against the terms of that order.

Marino has earned a reputation for stalking animal researchers in the past and encouraged violent action on her website, which also publishes photographs and addresses of scientists’ homes. For his part, Best has spoken internationally about the justification for extreme animal activism. As a consequence, he has been banned from entering the United Kingdom.

In his request for protection filed in Dona Ana County, New Mexico, Best described Marino as “an old friend”, saying that they had worked together in the past “for the animals”. But he said that Marino had developed a “fatal attraction, love/hate” relationship towards him. Best alleged that in the past several months Marino had harassed him by phone and e-mail, threatened his life and slandered his reputation online.

Best would not speak about the case to Nature, but wrote in his petition that he feared Marino could pose a physical threat to others. “I now fear that person will not be a medical researcher/vivisector she loathes so intensely, but rather me,” he said.

The New Mexico court granted Best’s protective order against Marino, requiring the woman to stay at least 100 yards (about 100 metres) from Best, his New Mexico home and his workplace. The order further required that Marino refrain from contacting Best, except through his lawyers.

“I don’t enjoy the fact that Dr. Best has been targeted, it’s just an ironic twist of fate,” says David Jentsch, a neuroscientist who works with animals at the University of California, Los Angeles. Jentsch obtained his own restraining order against Marino in 2010 after personal details about him appeared on her website.

Since becoming a target of Marino, Jentsch has followed the animal-rights movement closely, and he argues that Best has, in the past, advocated for the same kind of action against animal researchers that Camille Marino is now directing towards Best. Still, Jentsch says that everyone, including Best, deserves to exercise legal protections against stalking and threatening speech.

“If more often we get these orders and these people defy them and go to jail, cyberstalking and cyberbullying is going to diminish,” says Jentsch.

Marino is scheduled to be tried in Detroit, Michigan, on 14 November on separate charges of aggravated stalking against Donal O’Leary, a cardiovascular researcher at Wayne State University in Detroit, Michigan.