Contractual waiver of claim under the 1978 Yugoslav Code of Obligations

The paper analyses validity of contractual waiver under the Yugoslav Code of Obligations. Generally, the effect of a waiver of claim under the Code would be an obligation to refrain from exercising a certain right that may be invoked as defence against the waived claim. Under the Code of Obligations, a waiver of claim is generally valid. There are cases where validity of the waiver is explicitly excluded. Is a waiver invalid only in cases where it is expressly forbidden? If not, what would be the criteria under which, irrespective of the fact that there is no express prohibition, a waiver would nevertheless fail to produce effects? Are there additional criteria if a future claim is waived? This paper deals with these issues, seeking to set the criteria under which a (generally permitted) waiver of existing and future claims shall not be effective in a concrete case under the Code.