A leading member of the Shell to Sea campaign group, which is opposing the Corrib gas project in Co Mayo, has been jailed for seven months.
Pat O'Donnell, 52, a commercial fisherman from Porturlin, Belmullet was convicted of obstructing and using threatening and abusive behaviour towards gardaí on two separate occasions in September 2008.
The Circuit Criminal Court in Castlebar was told that O'Donnell and a group of around 30 others had surrounded an unmarked garda car.
They then threatened and intimidated four gardaí who had been monitoring a four-hour long protest.
During the incident, which occurred on 14 September 2008, the protesters hurled abuse at the gardaí.
The protestors prevented them from getting out of the car and demanded that they hand over a surveillance video camera.
Judge Raymond Groarke described the actions of the group as a dreadful event, which was clearly intended to intimidate the gardaí.
He told O'Donnell that he regarded him as a bully and a thug who believed he could do what he liked and get away with it.
The judge imposed consecutive sentences of three and four months on each of the two counts.
Another Shell to Sea campaigner who was involved in the incident, 46-year-old farmer Martin McDonnell from Bunalty, Glenamoy, was given a four-month suspended jail sentence and fined €500.
Two other members of the protest group, Tony King a 65-year-old farmer from Aughoose, Pullathomais and Kevin Moran an unemployed machine driver from Milltown, Glenamoy, were each fined €500 for public order offences.
Spokesperson for Dublin Shell to Sea Caoimhe Kerins said: 'This sentence is yet another example of the very harsh punishments being given to prominent anti-Shell campaigners for what are minor public order offences.
'The community living close to Shell's proposed experimental refinery is being criminalised for their opposition to this disastrous project.'
