The Dutch capital offers 35 public urinals for men compared with just three toilets designed for women.
Geerte Piening, 23, was caught short after a night out drinking in Amsterdam's vibrant Leidseplein in 2015. It was past closing time and the nearest public toilet was a couple of kilometres away, so she decided to find a quiet street while her friends kept watch.
She was caught by three police officers. "At the time I really didn't want to get involved in a discussion," she said. "But the next day I thought, just a minute, I'm going to fight this."
The judge, in this case a man, told her she should have used one of the men's facilities rather than resorting to urinating in public - an offence known as "wildplassen" in Dutch.
Using the word as a hashtag, some women mocked his suggestion and shared photos of themselves demonstrating the obvious difficulties involved in adapting to urinals.
Unlike men, women have no discreet way of using the metal structures.
The judge also likened the offence to throwing litter on the street rather than in a bin, prompting one commentator to point out that banana peels or chocolate bar wrappers could be stashed in a pocket and dumped at any point in a gender-neutral bin.
'Enormous feminist thing'
Ms Piening insisted she had used the alleyway only as a last resort and said public facilities for women in other European capitals were far superior.
"Isn't it embarrassing for a tourist city like Amsterdam that women have nowhere to go?" she told the AD newspaper,
"It wasn't my intention that this would become an enormous feminist thing. On the other hand, it's good it's being addressed."
The judge acknowledged there were fewer facilities for women but said the council was not obliged to provide them.
Women were less likely to use them anyway, he added, noting this was a rare case.
"You are only the second woman I've seen in court for this," he was quoted as saying.
Amsterdam city officials have questioned whether investing in public loos for women are worth the money
Amsterdam's city council said there had never been any policy on public toilets. "There are more men's than women's just because that's how it's gone," Peter Paul Ekker, a spokesman for the deputy mayor, told the BBC.
"Obviously it should be equal and everyone will agree it can be done better, but what are the costs, is there space, and is it worth it?"
But this may not be the end of the story.
A Facebook group has been set up encouraging women to join a protest on Friday, taking up the judge's challenge of using the men's urinals.
More than 5,000 people have so far expressed an interest in attending the event.
Organiser Cathelijne Hornstra says she wants to show the absurdity of crouching "with my buttocks protruding under the edge while half-drunk".
(By Anna Holligan - bbcnews.com)