A spouse can transfer his or her separate property and 1/2 of community property and quasi-community property. Problems arise when a spouse tries to transfer more than 1/2 of the community and quasi-community property by a Will or otherwise.
Forced / Widow's Election
When a deceased spouse attempts to transfer by Will more than his or her 1/2 interest in community property, the transfer is voidable by the surviving spouse. Although rarely used nowadays, in situations where one spouse is particularly wealthy, he or she may utilize a strategy to specify in the Will that all of the community property is to be held in an irrevocable trust for the benefit of the surviving spouse during her lifetime. The Will may further provide that the surviving spouse can either agree to this arrangement, or make an election to enforce the surviving spouse's right in 1/2 of the community property and give up the right to the lifetime benefit of the deceased 1/2 interest in community property. This is known as a "forced" or "widow's" election.
Aggregate vs Item Theory of Community Property
Sometimes the problem of transferring a specific item of community property may be handled by having spouses agree to using the aggregate theory of community property. The aggregate theory of community property essentially is the idea that each spouse owns 1/2 of the community property by value rather than by item. Therefore, under the aggregate theory, a spouse may bequeath 1/2 of his or her assets without making mention of a specific asset. Under the item theory, a spouse only has the power to dispose of his or her 1/2 interest in any particular community property asset. California's default rule is to follow the item theory unless the spouses agree in writing otherwise.
Although the subject of a deceased spouse transferring a surviving spouse's interest in community property may be fairly infrequent, this concept highlights an important point. A person may not dispose of assets that he or she does not actually own.