An attempted badger survey sparked an eight hour protest as Cilgwyn residents questioned the Welsh Assembly Government's right to enter their land.
Residents of Brithdir Mawr and Tir Ysbrydol alleged they had not been properly notified that officials were to enter their land, and they were unable to check the identity of the men because they were wearing black masks.
Around six police vans and cars full of officers were at the scene during the protest which lasted from 10am to 6pm.
Resident Emma Orbach said: "It's disgusting, this is totally without our permission.
"We have a history in this valley and we do not give up."
The masked men were finally escorted onto the land by police, while residents chanted "shame on you!", but left soon afterwards due to technical issues.
Officals said they would notify residents before their next visit.
Resident Felicia Ruperti said: "We will still protest when they come back. "I felt very intimidated by the amount of police here today. We have been peaceful from the start and have not threatened anyone."
A Welsh Assembly Government spokesperson said: "Our main aim is to lawfully carry out this work to identify where badger setts are in the area. Bovine TB is a crisis we have to deal with and we need to co-ordinate activity effectively."
"It has been made clear from the outset that the identity of contractors would not be put in the public domain. Clearly today the contractors tried to protect their identity because of their concern about the situation and level of personal intimidation. They felt that that their identity was not being respected by the media and individuals.
"In the last six years, 42% of cattle farms in the area have had bovine TB. We are serious about getting rid of bovine TB from the area and the activity needs to be planned and co-ordinated, which includes surveying all the land in the area for evidence of badger activity.
"Over 95% of the land has already been surveyed. The High Court has decided that the TB Eradication Order, which was challenged by the Badger Trust in Court, is lawful. The Welsh Assembly Government has the legal powers to access land to implement our badger control strategy.
"A very small minority of land owners are continuing to refuse access to the land. We have continued to engage with them including meeting some of the individuals concerned. We are very disappointed that a tiny minority have decided to engage in illegal activity."