The second half of 2025 was marked by the Cour de cassation’s recognition of a general duty of vigilance in environmental matters.
More precisely, by two decisions published in its official report (Cass. civ. 1st, 24 September 2025, no. 23-23.869; Cass. civ. 3rd, 13 November 2025, no. 24-10.954), the Cour de cassation endorsed the principle already enshrined by the Constitutional Council nearly fifteen years earlier, namely that “everyone is subject to a duty of vigilance with respect to harm to the environment that could result from his or her activity” (Cons. const., 8 April 2011, Michel Z., no. 2011-116 QPC).
This new standard of behavior requires anyone whose activities are likely to cause damage to the environment to take the necessary steps to identify and prevent such damage. A breach of this environmental vigilance obligation may expose the party in breach to tortious and contractual liability alike.
The scope of these two decisions is therefore significant. In particular, it should induce economic operators, when faced with uncertainty about the environmental risks posed by their activities, to document the positive vigilance and prudence measures they have implemented (scientific monitoring, definition of a rational risk-management strategy etc.).
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