Sean Binder is one of 24 aid workers who went on trial on Thursday (November 18) on the Greek Island of Lesbos, facing charges of spying and disclosing state secrets.
The trial was immediately adjourned amid calls from right groups and authorities to drop the "absurb" charges.
Outside the court on Thursday, Binder, who has already spent 107 days in pre-trial detention, waited for the trial to start with his mother.
"I feel angry. I feel angry that the legal requirement to try and help people in distress out at sea is being criminalized right now. I am angry because there is not a shred of evidence against us (...) Today there is no more search and rescue happening on the island of Lesbos and that is precisely because they criminalize it."
Amnesty International and Human Rights Watch say the trial is intended to intimidate aid workers from carrying out their work.
The European Parliament called the trial "the largest case of criminalization of solidarity in Europe" in a report in June.
The aid workers on trial were affiliated with the Emergency Response Center International - or ERCI - a nonprofit search-and-rescue group operating on Lesbos from 2016 to 2018.
They face up to eight years in prison, convertible to a fine.
Among those tried is Sarah Mardini, a Syrian refugee who took an overcrowded dinghy to Greece with her sister Yusra in 2015, at the height of Europe's refugee crisis.
She saved the other 19 passengers by pulling their sinking boat to shore for four hours.
Mardini now lives in Germany and is barred from entering Greece, something her lawyer called "a paradox."
The aid workers also face more serious felony charges, including people smuggling, belonging to a criminal group and money laundering, which carry 25-year prison sentences.
These charges are still being investigated.
73-year-old Dutch national Pieter Wittenberg is another volunteer on trial.
"Would I do it again? Yes of course. Why would I do it again? Because somebody has to do it."
The defendants deny the charges against them and are expected to plead not guilty.