Not exactly. Yes, your Will can say anything you want it to say. However, not everything you may write in your Will may be allowed under state law. The biggest thing that the state may have a say over would be if you wanted to disinherit your spouse. The state, if requested by your surviving spouse, can essentially force your estate to provide your surviving spouse a portion of your estate. This legal maneuver harkens back to English law concepts of dower or curtesy, both of which were designed to reserve portions of an estate for the surviving spouse to prevent that spouse from falling into poverty and becoming a burden on the community.
In South Dakota, the amount of the estate your surviving spouse can claim depends on how long you have been married with the maximum amount of 50% being reached at 15+ years of marriage. Your surviving spouse does not automatically receive this amount; he or she must affirmatively “elect” to take this share, but there are circumstances in which your surviving spouse may be forced to make this election, such as if they are receiving certain income or asset-based benefits.