Three anti-war protesters claim to have been served with legal notice by Aer Rianta threatening to have them imprisoned if they participate in any further protest at Shannon Airport.
The three include former Army officer Mr Edward Horgan, who recently failed in a High Court bid to prevent the use of the airport by US war planes en route to Iraq.
The other two men named in the notice are peace activists Mr Tim Hourigan and Mr Conor Cregan.
"This threat . . . may be a further attempt by Aer Rianta and the Government to silence protests and adverse publicity on the issues of further use of Shannon airport by the US military," the three said in a statement.
"Shannon has become a virtual US military base, protected by the Irish security forces. "It is necessary to continue to protest against Ireland's participation in crimes against humanity and to challenge attempts to prevent such peaceful and lawful protests," the statement said.
A demonstration has been planned at Shannon Airport next Saturday. The three men said they "intend to participate in this peaceful protest, if allowed to do so".