In court on Monday the prosecution called for fines of 5,000 euros plus 10,000 euros each on Sébastien Arsac, one of the founders of the L214 animal rights campaign, and Tony Duhamel, another member who helped him place video cameras in the slaughterhouse in Houdan, near Paris, in December.
The pair were caught when they went to fetch their cameras because one of them had fallen off, although they still managed to broadcast some of the footage on the group's website.
The abattoir's management, which is supported by a farmers' union, is demanding 219,000 euros in damages, claiming it has lost business and that its employees have received death threats.
Trespass, invasion of privacy charges
The defence rejects charges of trespass and invasion of privacy, claiming that the activists entered the plant through doors that were not locked and pointing out that the plaintiff is a company not an individual whose privacy might have been violated.
They have submitted a challenge that caused the trial to be postponed at a first hearing in June.
Prosecutors stressed that the abattoir and its methods were not on trial - although they will be in a separate case arising from a legal complaint filed by L214 - and claimed that the accused had stolen, lied, assaulted and broken the law.
The defendants admit having entered the building and placed the cameras in it but argue that their cause was just.