Women in the Indonesian city of Lhokseumawe have been banned from straddling motorbikes because of fears that it distracts men drivers.
Civic leaders in Aceh province, which is ruled by strict sharia law, have launched a crackdown on what they say are un-Islamic practices.
Apart from the side-saddle law other laws have been passed that prohibit women from wearing tight trousers, and permits flogging of homosexuals and stoning of adulterers.
Legislatorsd said that women sitting astride motorbikes was "improper". Mayor Suaidi Yahya said: "Women sitting on motorbikes must not sit astride because it will provoke the male driver.
"It's also to protect women from an undesirable condition.
"It's improper for women to sit astride. We implement Islamic law here."
The mayor told the Jakarta Globe that behaviour and morals were straying from Aceh's Islamic cultural values.
"We want to save women from things that will cause them to violate shariah law. We wish to honour women with this ban because they are delicate creatures," he said.
Women can straddle motorbikes if they are driving the vehicle, but only if they are dressed in a "Muslim way".
Aceh started implementing sharia law after it was granted autonomy in 2001.
The straddling ban will come into effect over the next few months and the government plans to distribute handouts to inform residents. Penalties for infringement have not been detailed.
Nanda, a student from Lhokseumawe's Malikussaleh University, said the new law was ridiculous. Straddling a bike was safer and more comfortable, she said.
Last month, 16 people were publicly flogged in front of the Grand Mosque Baitul Makmur Meulaboh for gambling and indecent behaviour.
Police chief Jhon Aswir said public flogging demonstrated the government's commitment to enforcing Islamic law.