Obtainable when playing as Ivo in Seastone.
In the Headmaster's Office when rescuing the frog, you'll find a seal on the desk. Use it to initially make three new laws - 'legalise smoking dried leaves', 'respect for pregnant elves', and 'only marry for love'.
The last law is part of the main quest and can be obtained when trying to get the magical amulet from the ogre, Blout. Travel back to the office and make a law against wearing magical items.