On Tuesday, Iranian men posted photos of themselves wearing headscarves to Facebook and Twitter with the hashtag #MenInHijab.

#MenInHijab highlights unequal standards of dress for men and women. In Iran, women are required to wear the headscarf, or hijab, as part of Iran’s Islamic dress code. The hijab must cover most of a woman’s hair. Citing the Iranian government, Vox news reports that 3.6 million women were warned, fined, or arrested in 2014 for “Crimes Against Public Prudency and Morality, ” which are “most often linked to dress code violations.”

Those in support of the dress code have committed violent attacks against women in Iran. In November 2014, acid attacks were carried out against more than 14 women in Esfahan. Campaign for Human Rights in Iran stated, “In a number of attacks, eyewitnesses reported that assailants proclaimed they were confronting improper hijab as they flung the acid.”

Iran’s religious authorities often reinforce the dress code for women. Last month, senior Shiite cleric Seyyed Youssef Tabanabi-nejad claimed that women dressing in a Western style caused Iran’s rivers to dry up.

One #MenInHijab participant, whose name remains unknown, wrote about his choice to take a photo of himself wearing hijab. “Forcing anyone to wear any sort of clothing is an insult to [anyone’s intelligence]. It is cruel, unjust, and humiliating.”