The two face charges of trespassing in an individual's home and invasion of privacy after being caught trying to retrieve their cameras from a slaughterhouse near Paris where Sébastien Arsac and Tony Duhamel had hidden them so as to film its procedure for killing pigs.
Arsac is one of the founders of the L214 animal rights group, which campaigns against the consumption of animal products.
The trial was suspended in June when their lawyers challenged the charges on the grounds that the "individual" in question is the company that operates the abattoir.
The court had the power to suspend Monday's proceedings if it judged the challenge sufficiently serious to pass it on to an appeals court.
"We're very confident," one of their lawyers, Caroline Lanty, told the AFP news agency. "My clients fell that they carried out useful actions, without causing damage or harming the employees."
The case is unusual since most videos broadcast by L214 are filmed by workers at the companies concerned, who have access to the premises.
The company in question is being investigated for animal cruelty in response to a legal complaint made by the campaign group.