The three cases are part of a campaign by Saudi women, who have been broadcasting daring videos with their cellphones, using Facebook to organize street protests and posting Twitter messages to challenge the very idea of male supremacy in their famously patriarchal society.

The campaign, started by a loose network of activists who have enlisted young, media-savvy women, has gone far beyond earlier protests against the kingdom’s reaffirmed ban on female drivers, and has become a challenge to the pervasive guardianship system. In this entrenched system of guardianship, a male relative — usually a father or a husband, but sometimes a brother or even a son — has the legal right to control a woman’s movements.

What use is the right to drive, the young activists ask, if a woman still needs a man’s permission to leave the house?

Even among some of the activists themselves, there has been surprise at the response. “I’m very impressed; a few years ago I thought I was the only one who thought this way,” said Moudi al-Johani, 26, a Saudi woman who said she was locked up by her family when she returned from Florida during a college vacation.

Ms. Johani’s father was angered by her independence and held her at home against her will for months, she said. She fled last year to the United States, where she has applied for asylum. She was among those who started an online campaign, #StopEnslavingSaudiWomen, which she claimed “has been trending for more than 230 days.”