A Fundamental Principle of Spanish Civil Law

Pacta sunt servanda is a fundamental principle of Civil Law that stipulates that contracts are binding and must be fulfilled without excuse or pretext. This principle is based on several theories:

1. Legal Voluntarism: Obligation arises from the sovereignty of the parties' will.

2. Ethics: It is based on good faith and not betraying the trust created.

3. Normativism (Kelsen): The obligation is grounded in a positive legal norm.

4. Private Autonomy: The contract is a manifestation of self-sovereignty to regulate legal situations.

Exceptions to the Principle

While the principle is firm, there are exceptions in the Civil Code, such as the dissolution of a partnership contract at the will of any partner, termination of a mandate for various reasons, and revocation of a donation for specific causes. Additionally, doctrine has developed theories for situations where unforeseen changes make contract performance extremely onerous:

1. Rebus sic stantibus Clause: Allows contract termination when there are significant changes in circumstances.

2. Theory of the Basis of the Business: Permits contract revision if the fundamental circumstances that led to the agreement change.

3. Theory of Unforeseeable Risk: Allows contract revision or termination in the face of unforeseeable events that make performance very burdensome.

International Application

In international law, the principle of pacta sunt servanda is equally crucial, obligating states to fulfill treaties and international agreements in good faith, as established by the 1969 Vienna Convention on the Law of Treaties.

Remember that...

The principle of pacta sunt servanda ensures contractual stability, but the law offers flexibility through reasonable exceptions to ensure justice in changing situations.