Legal Question in Business Law in California

When you say "owns a business," I'm assuming you mean that the business is the woman's separate property, and it is not community property to any significant extent.

The answer is no, not usually. A husband has no power to deal with the wife's separate property, and vice-versa. It would take a court order - which most judges would be very hesitant to make - or some kind of a still valid and pre-existing agreement, such as a prenuptial agreement regarding the business. Since you mentioned that there is no power of attorney, I assume there is also no other agreement in writing.

When the woman dies, the business will pass to her heirs under her will or trust. If there is no will or trust, the business and any other separate property she had will pass under the rules giverning intestate succession, and the husband will be in line to receive some of it, the percentage depending upon how many children, etc. the deceased woman had.

Sometimes separate property acquires a partial community interest. This can happen with a separate-property business when it is actively operated by a married person during marriage. The longer the marriage and the more the value of the business is due to the labors of the married person during marriage, the greater the community interest. Lawyers that practice in the specialty "family law" or divorce lawyers, and probably many wills-trusts-estates lawyers have special software that they use to calculate the community interest under such circumstances.