Sean Clerkin, 64, was arrested and has been charged under the Terrorism Act, after he displayed a placard stating Genocide in Palestine Time to Take Action.
The protester was taken to a police station and held for around three hours.
Speaking to the Glasgow Times after he was released, he said he had to sign a “draconian” undertaking.
He said: “I had to agree not to enter an exclusion zone which covers the city centre.
“I was charged under section 13 of the Terrorism Act and given a date to appear in court.
“I am effectively banned from the city centre for the duration until the court date.
“If I go into the city centre, I will be jailed.”
He said he will comply with the undertaking.
He added: “I will abide by it but I think it is draconian and we are on the way to a politicised police state.”
Mr Clerkin was arrested in Nelson Mandela Place on Friday around noon after he displayed the sign.
(Image: GT)
The words Palestine and Action were in much larger text than the rest of the sign.
The group Palestine Action is a proscribed organisation in the UK.
Two men displayed the sign and were warned by police officers they were “demonstrating support for a proscribed organisation”.
They were warned that the way the sign was written was deliberately intended to “circumvent the law”.
When it was displayed again minutes later, as a third protester made a speech, two police officers moved in and made an arrest.
Mr Clerkin was taken to a nearby police van amid shouts of “let him go” from supporters.
The man stated repeatedly as he was taken to the police van: “I am not a terrorist”.
The city centre protest on Friday was calling for “an end to the proscription of Palestine Action and “the end to genocide in Gaza And Palestine.
Other protesters criticised the arrest.
Mick Napier of Scottish Palestine Solidarity Campaign, said: “This is the theatre of the absurd. You can’t say Palestine and genocide in the same sentence.”
The incident follows Police Scotland charged a man under suspicion of terror offences for wearing a T-shirt allegedly showing support for the proscribed group Palestine Action.
It is understood that the 55-year-old activist was leafleting near the TRNSMT festival, in Glasgow, when police charged him.
A Police Scotland spokesperson said: “A 64-year-old man has been arrested and charged in connection with an offence under the Terrorism Act for displaying a sign expressing support for a proscribed organisation.
“Officers were called to a protest at Nelson Mandela Place in Glasgow at around 9.50am on Friday, 18 July, 2025.
“The man is expected to appear in court at a later date.”