The founder of pro-Brexit campaign group BeLeave has won his appeal against a £20,000 fine imposed by the Electoral Commission.
Twenty-five-year-old Darren Grimes was handed the fine in 2018 after being accused of breaching spending rules during the EU referendum campaign three years ago.
He insisted he was "completely innocent" and raised £93,956 via online crowdfunding to appeal the Commission's verdict.
Mayor's and City of London Court heard that the Commission had misinterpreted the law and set a key legal test "too high" on whether BeLeave had been correctly registered on official forms.
Mr Grimes's lawyers said he had filled out the complex and difficult-to-understand forms to the best of his ability.
The judge said Mr Grimes had tried to meet his obligations to the Commission in filling out the forms, and that his actions were not dishonest or lacking transparency.
Following the ruling, Mr Grimes hit out at the Commission on Twitter.
"The Electoral Commission's case was based on an incorrectly ticked box on an application form - something that it had been aware of for over two years and had not been raised in two previous investigations," he wrote.
"Yet the Commission still saw fit to issue an excessive fine and to spend almost half a million in taxpayer cash pursuing me through the courts. This raises serious questions about its conduct both during and after the referendum."
He continued: "It's vital that more young people are encouraged to get involved in politics and make their voices heard. I just hope that the punitive actions of the Electoral Commission don't put my generation off from engaging in our democracy."
The Electoral Commission said they were "disappointed" with the outcome.