In most countries in the world it's unremarkable when women plan to get behind the wheel and drive, but in Saudi Arabia when thousands of women do so on Saturday, it will be a massive act of rebellion in the face of the country's religious authorities. 

Thanks to Twitter, Facebook, and other forms of social media, organizers say around 16,000 people have signed the petition calling for the elimination of the ban on women drivers and organizers hope that momentum carries over to Saturday's protest. "Now the mainstream press is getting involved too — itself a telling indication that the official climate is becoming more tolerant on this issue, The Guardian explains

Tomorrow's drive comes after months of planning — the petition and organization for the "day of defiance" began gaining traction in September when it garnered over 12,000 signatures — and after two decades of  law. CNN reports: 

An informal Saudi ban on driving became official policy in November 1990 during the Gulf War. As female American soldiers based in Saudi Arabia drove freely through military bases, 47 Saudi women organized a convoy to drive the streets of Riyadh in protest against the law that restricted them. Officials arrested them and suspended many from their jobs.

Neither sharia law nor national traffic regulations explicitly ban women from driving, but women are not issued licenses, The Guardian adds, so they cannot drive legally.

Late last month, a high-ranking cleric named Sheikh Saleh bin Saad al-Lohaidan said that driving hurts women's ovaries. "If a woman drives a car, not out of pure necessity, that could have negative physiological impacts as functional and physiological medical studies show that it automatically affects the ovaries and pushes the pelvis upwards," he said, in an interview translated by Reuters. Using al-Lohaidan's logic, it would seem that a woman's body or an automobile know when a woman is driving out of pure necessity versus a whim. 

The campaign to get women driving, Women2Drive, started in 2011. "Scores drove, and many were stopped by traffic police," CNN reports, explaining that one woman was even sentenced to 10 lashes. Because of the spread of social media (one example: Saudi women have been posting videos of themselves driving) and some changes in laws  — women will be able to be candidates and vote in municipal elections come 2015 — in Saudi Arabia, this year's drive is expected to be bigger.