The principle of conscientiousness and fairness requires participants in obligations relationships to mutually consider individual or common interests and to act conscientiously and fairly when entering into contractual relationships so as not to harm the interests of other participants.49
Cigoj50 defines the obligation of conscientious and fair conduct as one of the moral principles. Strohsack opposes this view, arguing that acting in accordance with morality represents an absolute and general (including abstract) rule for the conduct of all participants in obligations relationships, whereas acting in accordance with the principle of conscientiousness and fairness constitutes a specific rule for each individual participant in a specific obligations relationship. Therefore, not every violation of the principle of conscientiousness and fairness is also a violation of morality. The significance of this principle lies in its focus on the conduct of obligations subjects, without granting courts the authority for arbitrary decisions beyond the law. It allows courts to mitigate the potential harshness of certain provisions based on the specific circumstances of a given case and align them with moral standards. According to Plavšak, this principle serves as an argument in the application of the law, in the selection of appropriate legal rules, and in determining their content for a particular case. It is also concretised in specific institutes of the OZ, such as liability for unfair negotiations (Article 20 OZ) or the nullity of certain provisions of general terms and conditions (Article 121 OZ).
Examples in which courts refer to conscientiousness and fairness show that it primarily functions as a guiding principle for the application and interpretation of legal rules. Based on Supreme Court judgment II Ips 66/2002, one might conclude that the court rejects the direct application of the principle of conscientiousness and fairness. However, I believe this is not the case, as evidenced by a more recent Supreme Court decision in case II Ips 281/2009. In my view, the latter stance is more accurate, considering that the principle of conscientiousness and fairness cannot be enforced other than at a general level. Moreover, its direct application is not explicitly excluded by law, unlike the principle of equal value of performances. We can conclude that, while cases in Slovenian jurisprudence where the principle of conscientiousness and fairness serves as a standard for independently determining permissible or prohibited conduct are rare, such an application cannot be ruled out. The criteria used to define conscientious and fair conduct include: the type and content of the contractual obligation, the characteristics of the opposing party, a particularly blatant disregard for the interests of the other party, contractual clauses, or other conduct that is unreasonably advantageous to only one party, etc.51
It is important to emphasise that the principle of conscientiousness and fairness establishes a value-oriented guideline for the conduct of parties in all aspects of business obligations relationships,52 This applies to contract formation, the exercise of rights acquired through the conclusion of a contract, and the fulfilment of obligations assumed under a contract.53 In contract formation, this principle is reflected in various European legal systems through explanatory obligations, liability for unjustified termination of negotiations, and rules on the voidability of contracts due to defects in intent, which prioritise the interests of the fair party over those of the unfair party. In the exercise of rights, it is closely linked to the prohibition of abuse of rights,54 while in the fulfilment of obligations, it is typically realised through notification duties.55
