Six environmental organisations will be challenging the deed through which the government granted guardianship of Miżieb and Aħrax to hunters, the groups announced on Friday.
Two separate court actions representing the parties were filed in front of the Tribunal for Administrative Revision on Thursday.
The NGOs are Birdlife Malta, Moviment Graffitti, Din L-Art Helwa, Friends of the Earth (Malta), Flimkien Ghal Ambjent Ahjar and The Ramblers' Association of Malta.
The NGOs are claiming the Lands Authority has acted in an "arbitrary, intransparent, discriminatory and unreasonable manner" and that it has committed "numerous procedural violations" resulting in it acting outside its powers as established by law.
"The irrelevant and improper considerations used by the Lands Authority to assess and award the concession will result in the public's enjoyment of the countryside found in these sites to be curtailed for large swathes of the year, all to accommodate a minority of FKNK's members," the NGOs said in a statement.
The NGOs assert that EU law was breached when the government failed to conduct any of the required studies in order to determine and evaluate the environmental impacts of such a large concession.
They also claim EU law was also not followed when the public was not allowed to participate in the drafting of the resulting management plans due to the fact that the agreement was negotiated in secret.
The NGOs said the concession of the two areas for the "risible sum" of €400 to entertain a pastime will also result in lost revenue which should have been accrued towards the Environment Fund.
"The deed is also being challenged on the grounds that it requires the minister responsible for hunting to employ a number of 'conservation officers' from the public purse who will then be managed by FKNK. It is being claimed that since a minister is not a public officer at law, he has no legal power to directly employ people into the public service for this purpose," the six groups said.
A sit-down protest in front of Castille is being organised by the groups on Saturday morning.