Karen Pierce’s protest was registered with senior levels of the State Department and the White House was informed, following the arrest of The Independent’s chief US correspondent.
Andrew Buncombe was shackled, assaulted and detained for more than six hours after being accused of “failing to disperse” in Seattle.
He denies committing an offence but now faces a maximum penalty of 364 days in jail and a $5,000 (£4,000) fine.
Mr Buncombe was covering the police operation to clear the Capitol Hill Occupied Protest – where an area of Seattle had been occupied by demonstrators since early June.
The journalist wrote that he was arrested five minutes after arriving at Cal Anderson Park by an officer who told him to stop taking photographs and leave.
He was handcuffed, shackled and taken into custody at the West Precinct station, where he described crowded and unsanitary conditions despite the coronavirus pandemic.
Mr Buncombe said he was assaulted by a guard, while other inmates said they had been threatened, mistreated or accused of crimes they did not commit.
He said he was alone at the time of his arrest, remained on the correct side of a police cordon, repeatedly identified himself as a journalist and showed his press badge issued by the State Department’s Foreign Press Centres.
The arrest sparked international condemnation, amid concern over police action against more than 60 other journalists covering George Floyd protests in the US and Donald Trump’s anti-media rhetoric.
A member of Seattle City Council has written to mayor Jenny Durkan and police chief Carmen Best demanding action on Mr Buncombe’s “unacceptable” treatment.
Councillor Lisa Herbold said it violated the Seattle Municipal Code, which states that failure to disperse orders cannot apply to news reporters unless they are “physically obstructing” lawful efforts by police to disperse a group.
The city council also adopted a bill in 2017 that enshrined the right of “public observation, recording or expression in the vicinity of police actions”.
“It is our job as elected officials to ensure the press remains free and is able to carry out its work, in accordance with the constitution and city law,” Ms Herbold wrote.
“The constitution and municipal code protections for the press, and observers, do not exist for the convenience of government, to be cast aside whenever they happen to be inconvenient.”
The non-partisan councillor said first amendment protections for the press were a “linchpin of American democracy”, warning: “Unless respected by government, the quality of our democracy is diminished and eroded.”
Amnesty International USA said Mr Buncombe was one of at least 60 journalists arrested while covering protests sparked by the killing of George Floyd in May.
“The media have a right to attend and report on these protests, and law enforcement officials have a responsibility not to prevent or obstruct their work,” said deputy director of research Justin Mazzola.
“If not, human rights violations like the ones we have witnessed over the past two months will breed in the darkness.”
Christian Broughton, editor of The Independent, described Mr Buncombe as an “experienced and highly respected reporter”.
“As he writes in his article, the job of a journalist is not to disperse. Our job is to be present,” he added.
“It is imperative that democratic leaders everywhere stand up unequivocally for truly independent journalism. The arrest and appalling treatment of Andrew Buncombe must be condemned.”