(Source: The Law of Administrative contracts Teaching Material
Provisions of the law that govern the object of contracts in general require the parties to conclude a contract that has a possible, defined and lawful object. On top of that, Articles 3170 and 3171 deal with lack of object and unlawfulness of object. But within the realms of unlawfulness of object, Art. 3143 prescribes aggravated failures to comply with administrative laws or regulations that dictate about the necessities of authorization. As to Art. 3143 such a contract concluded in the absence of an authorization shall be of no effect as if the object of the contract is unlawful. The assumption here is the agency is acting ultra vires.
Absence of Object
There is no mistake in holding to the effect that when an object (cause) is absent from a contract when the object is an impossible object in the first place. Thus if parties agree to do or to refrain to do a certain act which in reality is impossible the law considers such a contract as a contract without object. Absence manifests itself at least in two ways. An object might be absent from the beginning or the object of a contract may vanish in the course of time. Let us see Art. 3170.
A contract shall be null on the ground of lack of cause where, at the time when it is made, it makes it impossible to attain the result desired by the administrative authorities and known to the other contracting party.
Art.3170 views the object of the contract from the angle of the rationales of administrative contracts. Because administrative contracts are concluded aiming at serving the public, a public that cannot be properly served for reasons mentioned in our introduction if left in the hands of private individuals. Thus the object of administrative contracts should be purposive. And this purpose is all about serving the public via administrative contracts. Accordingly,” … the result desired by the administrative authorities…” thereof is this issue of purposive ness”
Hence if an administrative contract “makes it impossible to attain the result desired...” then the contract will be considered as lacking cause. Now read Art. 3170 again and consider the above discussion.
Unlawfulness of Object
As mentioned earlier an object of any contract should be possible as it should also be lawful. Art. 1716(1) reads “[a] contract shall be of no effect where the obligations of the parties or one of them are unlawful or immoral.”
This being the general rule, the picture changes when we consider administrative contracts as envisaged under Art. 3171. As opposed to Art 1717 which says “the motive for which the parties entered into a contract shall not be taken in to account in determining the unlawful or immoral nature of their obligations”, Art. 3171(1) basically views the nature of the object from the perspective of its motive. Thus, a contract shall be null on the ground of unlawful cause where it is made by the administrative authorities with [an unlawful object in view.] (Art.3171 (1))
One instance of unlawful motive is available under art.3171 (2). If the “ contract is made by the administrative authorities with a view to procuring advantages of a pecuniary nature to the other contracting party and not for a reason of general interest” then such a view is an unlawful view which plays in favor of nullifying the contract. As per the clarifications of view on this matter by Rene David, “these two Articles (i.e. 3170 and 3171) are devised to protect public interest from possible mistakes committed by administrative authorities and the dealings made by authorities and individuals to thwart public interest and promote individual interest”. These two provisions are not sufficient to avoid the potential dealings. This is even conceded by the drafter of the civil code. However, Rene David tries to mitigate the issue by calling upon the liberal economic system that the country was following. As such he argued by saying too much intervention seems impossible.