However, the airport says protester Bruce Mahalski, of Dunedin, knew about the consequences and declined an opportunity to move his demonstration outside.
Mr Mahalski was trespassed from the airport for two years on Tuesday after refusing to leave the terminal where he was standing with a sign reading: "It’s a Climate Emergency!".
He said the airport’s response was excessive.
"If I return within two years, it’s a $1000 fine or three months in jail for holding an A3 sign saying ‘it’s a climate emergency’ at the airport, which I think is pretty disproportionate," Mr Mahalski said.
His protest was developed with artist and scientist Craig Hilton, who documented people’s reactions to Mr Mahalski and his sign.
Mr Mahalski said he told airport staff about the protest when the pair arrived; initially there seemed to be no issue.
"But as soon as I started standing in front of where people were sort of dribbling out of the Jetstar flight that had landed, there was a problem," he said.
"And so we were both asked to leave.
"I said, no, I thought I was quite within in my rights, given the airport was owned by the government and the [Dunedin City Council] who have declared a climate emergency.
He acknowledged people did have to fly for family or business reasons but the airport’s reaction said "a lot about free speech, the right to protest, and its erosion at the moment".
"I just want people to know the amount of emissions they’re creating and have a think about it before they go on a flight.
"We are in the middle of the biggest existential crisis to face humanity."
A Dunedin Airport spokeswoman said the organisation respected the right to peaceful protest but any activity on airport grounds had to align with safety, security and operational regulations.
"Airport staff courteously advised the individuals that they could finish taking photographs but would need to move their demonstration to the designated area outside the terminal," she said.
"One individual chose to leave voluntarily — the other, after receiving two formal requests to relocate and being advised of potential consequences, declined to comply.
"As a result, the individual was trespassed by New Zealand Police, who were present on site."
She did not respond to Mr Mahalski’s specific comments on the airport’s reaction.
