Followers of four Yorkshire hunts had tried to hijack the North Yorkshire Moors Railway train on which local Labour MP Lawrie Quinn, who voted for the ban, was travelling on Saturday between Whitby and Pickering.
Horses were ridden onto the track, and one supporter lay down on the lines.
Philip Benham, the privately run railway's general manager, said: "People have their opinions and they have the right to express them.
"But what they did was, frankly, absolute stupidity.
"They were putting themselves and the people on the train at risk, it was unnecessary and extremely dangerous. We have informed the police and I will be talking to them again, although I do not know what the course of action will be.
"However, anyone who goes on to railway lines without permission is breaking the law."
Mary Holt, a member of the Sinnington Hunt for 20 years who initially had laid down on the tracks, said: "Lawrie Quinn has not been prepared to listen to the views of his constituents, he has had complete tunnel vision.
"We want to get the Bill repealed, it is both impractical and illogical," said Mrs Holt, of Kirkbymoorside, who was there with her husband James, also a hunt member.
Mr Quinn was a guest on one of the first steam services to run between Whitby and Pickering for two years after completion of track repairs allowing the heavy locomotives to run on the route.
Mr Quinn, Labour MP for Whitby and Scarborough, said: "I cannot understand what this minority was trying to prove. If this had happened on the outskirts of Leeds, there would have been outrage because of the anti-social behaviour. These people are supposed to be law-abiding citizens.
"The horses were being ridden very close to the train, and it must have been terrifying for them. If whoever is responsible wants to be brave, they should make themselves known to the North Yorkshire Moors Railway.
"My concern was for the people who were on board the train, it would have been unthinkable if the train had derailed."
Acting Sgt Mike Pannett from North Yorkshire Police, who were called by worried passengers, confirmed there had not been any arrests.
"There could have been one or two people who could have been stupid, but fortunately everything passed off without too much incident.
"It was a peaceful protest and these people, like anyone else, have the right to have their views heard, as long as it is in a law-abiding manner," he said.
paul.jeeves@ypn.co.uk