London Mayor Sadiq Khan is so distressed by Twitter’s reinstatement of Donald Trump’s account that he has called for increasing censorship on social media and requiring the former president to sign a “binding code of conduct.”

“The return of Donald Trump to Twitter shows why we desperately need new regulation of social media and online speech,” Khan tweeted on Sunday. “Freedom of speech is vital, but it must be balanced against keeping other people safe to protect our democracy and society.”

Billionaire Tesla CEO Elon Musk, who acquired Twitter in a $44 billion takeover last month, ended Trump’s long banishment from the platform on Saturday. The then-president was banned from Twitter and other major platforms in January 2021, after the US Capitol riot. Musk conducted a Twitter poll asking users whether Trump should be allowed to return. The survey attracted more than 15 million votes, 51.8% of which favored reinstatement.

Khan called Trump “a dangerous, far-right politician who has a history of inciting violence. He must not be allowed to use social media to preach hate and further fuel the politics of division.” He claimed that the former president put people at risk of hate crimes and “encouraged an attempt to overthrow the democratically elected US government.”

“We already know it could happen again if he’s allowed back,” the mayor added. “He should not be given access to a huge platform to continue spreading hate and undermining democracy without at the very least signing a binding code of conduct leading to his immediate removal if broken.”

Trump said on Saturday that he doesn’t “see any reason” to resume using Twitter, as he has built a strong following on his own platform, Truth Social.