Killarney's traditional jarveys are upset over the erection of a large bollard across one of their routes at Ross Castle, Killarney, part of the Killarney National Park.
This is the latest of several blockages in recent years, according to the jarveys.
Mr Billy Tangney, a leading member of the Killarney (Town) Jarvey Association, said the bollards went up in the last week without consultation or communication from the OPW.
The blockade will cut off an essential leg of the town to the Killarney waterbus journey on Lough Lein which begins at Ross Castle, he said. Mr Tangney said the jarveys were seeking legal advice on a course of action and would meet in the next days.
Already, the jarveys have lost a traditional route through the Demesne area, part of the national park, to the Killarney Golf and Fishing Club, and their territory has shrunk, Killarney town councillor, Mr Seán Counihan, (Lab), said.
Some of the longer trips are no longer popular and the jarveys rely on the short routes near the town, he said.
"The jarveys are synonymous with Killarney. We have to ask what is really going on here. The jarveys are being restricted to a smaller and smaller area," Cllr Counihan said.
A spokesman for the OPW has denied the measures were designed to restrict jarveys. The raising of a bollard at Ross Castle was to facilitate improvement works to the castle and the car parks and these were agreed with the town council, he said.
In fact, the OPW had invested in two brushing machines to clean the roadways of horse droppings to silence complaints about jarvey traffic in the national park, and the cleaning had been successful.