Why would the authorities in an agricultural society have official laws governing marriage?

The authorities in an agricultural society would have official laws governing marriage to ensure that the land and resources are passed down to the next generation in an orderly and fair manner. This would help to ensure that the land and resources are not concentrated in the hands of a few families, and that the society as a whole can benefit from the resources. Additionally, laws governing marriage would help to ensure that the society's values and traditions are upheld.