Ever since the Islamic Revolution of 1979, women in Iran have been required to wear the hijab in public. However, an increasing number of Muslim women are kicking back against the ruling – by refusing to wear a headscarf while driving.

According to the Guardian’s Iran correspondent Saeed Kamali Dehghan, it is now commonplace to see women driving with their hijabs untied and resting on their shoulders in Tehran, the Iranian capital. And while it might sound like a small act of rebellion, it is infuriating Iran’s “morality police”.

Formally known as Gasht-e Ershad, the morality police are undercover agents hired to enforce Islamic rules in public. They focus predominantly on making sure that women are observing hijab, resulting in the arrests of hundreds and sometimes thousands of Iranian women during the summer months.

Most of these women are urban, educated and middle-class, and stand accused of the crime of wearing “bad hijab” (where the headscarf is pushed as far back on the head as possible). Women who drive with their hijabs loosely tied are regularly stopped and fined, or have their cars seized.

Despite this, police are finding it difficult to force women to wear headscarves in their own cars – in part because of a thorny debate about whether a car constitutes public or private space.

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“What is visible to the public eye is not private space and norms and the rules should be respected within cars,” said Saeid Montazeralmahdi, a spokesperson for the Iranian police.

He warned that drivers should not try to get around this “norm” by tinting their car windows.

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Meanwhile, Hadi Sadeghi, the deputy head of Iran’s judiciary chief, said recently that “the invisible part of the car, such as the trunk, is a private space, but this does not apply to the visible parts of the car.”

Sadeghi’s comments sparked widespread mockery and condemnation on social media. One Twitter user posting a photo of a couple squeezed into the boot of a car, with the caption: “When you say only this part of a car is private.”

However, even Iran’s president, the moderate Hassan Rouhani, has argued that the police should respect people’s private space. Rouhani opposes a crackdown on women wearing the hijab, and has stated that he does not believe it is the police force’s job to enforce Islam.

“The police can’t do something and say I’m doing this because God said so,” the president said in 2015. “That’s not a police [officer’s] business.”

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Iranian lawyer Hossein Ahmadiniaz told the state news agency Irna that it was not up to police to define what counts as a private space.

“The law says that the space within a car is a private space,” he said. “The government’s citizen’s rights charter [launched by Rouhani] also considers a car to be a private space and it is incumbent upon enforcers to respect that.”

As well as covering their hair, women in Iran were ordered to stop using make-up and wear knee-length manteaus (a long, loose coat or over-shirt) when the late Ayatollah Khomeini came to power in 1979. More than 100,000 Iranian women and men protested against the new law when it came into force, and opposition to it has never died out.

The current debate about hijabs in cars comes hot on the heels of other protests against Iran’s stringent dress codes. In June, hundreds of Iranian women posted photos of themselves wearing white headscarves and other pieces of white clothing on social media, as a symbol of their opposition to the imposed hijab. Campaigners used the hashtag #WhiteWednesdays.

One contributor, who filmed herself walking down a main road wearing a white hijab, said that she was “so pumped up to be in this campaign.

“I want to talk to you of my imprisonment... they imposed hijab on me since I was seven,” she said, shaking her headscarf loose, “while I never felt committed to it and won't be.”

Images: Rex Features, twitter.com/masihpooyan