The board found the former president’s posts during the Capitol riot “severely” violated Facebook’s rules and “encouraged and legitimised violence”.
But it also criticised the company for violating its own rules by issuing an “indefinite” suspension, stressing it could not “make up the rules as it goes”.
The board issued a six-month deadline to review the decision and make a new ruling.
It listed two options: a time-limited ban or account deletion.
“Facebook cannot make up the rules as it goes, and anyone concerned about its power should be concerned about allowing this,” the board said, in a series of Twitter posts.
“Having clear rules that apply to all users and Facebook is essential for ensuring the company treats users fairly. This is what the board stands for.”
The company-appointed panel called for a review into Facebook’s general “contribution to the narrative of electoral fraud and political tensions that led to the events of January 6” and urged a rethink of the way world leaders and important figures were dealt with.
“The ‘newsworthiness’ of a public figure’s remarks should never take priority over urgent action to prevent harm,” the panel wrote.
“Facebook must be far more transparent about how its newsworthiness policy works.”
The Californian company was urged to ensure it issued a time-limited suspension or deleted the account of a head of state or high government official if they repeatedly posted messages risking harm under international human rights norms.
That suspension could be extended if the risk remained.
“Restrictions on speech are often imposed by powerful state actors against dissidents and political oppositions,” the board wrote.
“Facebook must resist pressure from governments to silence political opposition, and stand up for free expression.”
Trump ‘severely violated’ content standards
The board agreed with Facebook that two of Mr Trump’s January 6 posts “severely violated” the content standards of both Facebook and Instagram.
“We love you. You’re very special,” he said in the first post, and “great patriots” and “remember this day forever” in the second.
Those violated Facebook’s rules against praising or supporting people engaged in violence, the board said.
Helle Thorning-Schmidt, a former Danish prime minister who sits on the board, said in a conference call with reporters that Facebook shirked its responsibility to enforce its own rules.
“Facebook should either permanently disable Trump’s account or propose a suspension for a specific period of time,” she said.
The board said if Facebook decided to restore Trump’s accounts, the company must be able to promptly address further violations.
A Trump spokesman did not immediately respond to a request for comment.
What is the Facebook Oversight Board?
The board, which has 20 members and will eventually grow to 40, did not reveal how it voted.
It said a minority of members emphasised that Facebook should require users who seek reinstatement after being suspended to “recognise their wrongdoing and commit to observing the rules in the future.”
Facebook set up the oversight panel to act as the ultimate referee on content decisions, amid furious criticism about its inability to respond to a tide of misinformation, hate speech and other harmful content.
The board is empowered to make binding rulings on issues such as whether posts or ads violate the company’s rules.
The social media giant regularly takes down thousands of posts and accounts.
Since it was launched in October, the board has received some 300,000 appeals from users over content decisions but it’s prioritising cases that have the potential to affect many users around the world.
It has overturned decisions in five of the seven cases it has ruled on so far.
Mr Trump has also been permanently banned from Twitter.