The protest came days after conservative politicians' vehement opposition blocked an attempt to cement the decree's provisions in law.
Most of international force that ousted the Taliban is now preparing to withdraw by the end of next year and activists fear an erosion of women's rights will follow if hardliners pressure the elected government.
More than 200 young men protested in front of Kabul University against the decree on Elimination of Violence Against Women, which includes a ban on child marriage and forced marriage, makes domestic violence a crime and says rape victims cannot be prosecuted for adultery. It also outlaws "ba'ad", a traditional practice of exchanging women or girls to settle disputes or debts.
Protester Fazel Hadi, 25, said the decree was "imposed by foreigners" and broke Islamic Shariah law.
Mawladad Jalali, the mullah of the university mosque and one of the organisers of the protest, led chants criticising democracy in general and the women's law specifically. "Our main demand is that this law should be repealed in the parliament," he said before leading a brief march while police who cordoned off the area looked on.
Afghan president Hamid Karzai issued the decree on women's rights three years ago in a raft of commitments to international donors, but politician and activist Fawzia Kofi wanted to pass it in parliament to prevent any future president from reversing it.
The brief parliamentary debate on Saturday was ended by the speaker after fierce opposition from conservatives who said several provisions - including the ban on child marriage and jail time for domestic abuse - violated Islamic law. The decree remains in force, but the debate appears to have galvanised opposition to it.
The United Nations' mission in Afghanistan this week urged the government to do more to enforce the women's rights decree, saying it is only applied sporadically when women report abuse. "It is imperative for the development of Afghanistan that women are able to exercise their rights and be free from violence in their homes and workplaces," UN Special Representative Jan Kubis said.