When referring to the effectiveness of the law in a traditional sense, at first “contracts” seem to have little to do with the topic envisaged here; namely, “the effectiveness of environmental law”. The concept of effectiveness, “effectivité” in French, described by the Doyen Carbonnier as “the effective application” of legal rules, primarily invites us to look at whether the law is in fact applied and, in order to achieve this, to question the process of implementation, which involves both obligations and sanctions. Given that contracts are voluntary legal instruments, which, by an agreement of two or more willing parties, lead to the performance of various obligations, it seems that they cannot contribute to this process of the implementation of environmental law. Indeed, in addition to the fact that contracts relate mostly to interpersonal dealings that are only a little focused on the general environmental interest, given that they are solely based on the will of the parties, it could seem at first glance that they would afford little support to environmental law with regards to its implementation.

Yet, when we take a closer look at positive law, contracts now play a significant role in environmental law. Various studies have focused on contracts and have shown that they are becoming an essential regulation tool for environmental policies at the domestic, international or European levels, given that they can replace, anticipate, supplement or implement the law or can even make up for its shortcomings. In fact, a large and diverse range of contracts has been revealed: Natura 2000 contracts, carbon contracts, contracts for the sale of contaminated land, insurance contracts relating to environmental damage, waste disposal agreements, neighbourhood protection contracts, bioprospecting contracts, implementation contracts related to the international REDD system, rural leases with environmental clauses, energy performance contracts, agri-environmental contracts, conservation easements, ecological compensation agreements, provision of environmental services, public or private sustainable procurement, etc.

This list is long and not exhaustive and it does, in fact, relate to the effectiveness of environmental law. Indeed, all of these examples reveal the same dimension of effectiveness: the implementation of the objectives of environmental law, from the prevention to the remediation of damage. This is relevant here as it can be noted that a number of these contracts are prescribed by the legislator.