1, the law does not prohibit both husband and wife from signing a marriage guarantee, so the marriage guarantee itself does not violate the mandatory provisions of the law and should be effective. Moreover, according to the law, husband and wife have the obligation of mutual loyalty, such as agreeing not to cheat and not to have an affair;
2, if the violation should bear the consequences according to the agreement, but if there is an agreement not to divorce, because it violates the principle of freedom of marriage, it is confirmed to be invalid. In other words, the guarantee can be valid, but the provisions that violate the law will be confirmed invalid.
To make a marriage relationship legally effective, three conditions must be met:
1, the letter of guarantee in marriage is the true meaning of one party;
2. The content of the marriage guarantee does not violate the relevant provisions of laws and regulations;
3. The content of the marriage guarantee does not violate the principle of public order and good customs.
Legal basis: Article 135 of the Civil Code of People's Republic of China (PRC).
A civil juristic act may take written form, oral form or other forms; Where laws and administrative regulations stipulate or the parties agree to adopt a specific form, it shall adopt a specific form.
Article 136
A civil juristic act shall take effect upon its establishment, except as otherwise provided by law or agreed by the parties.
Without the legal provisions or the consent of the other party, the actor may not change or terminate the civil juristic act.