In the United States, most intellectual property is a creature of federal law, but state courts in divorce actions may divide the rights to it. The division and distribution of patents and copyrights is a question of applicable state law regarding marital property.
Intellectual property rights are most certainly marital when marital funds are used "in the creation process."
The classification, division and distribution of some intellectual property, such as copyrights on books, may be problematic because these intellectual efforts may have begun before marriage and continued during and after it.