Divorce

Yes, a spouse can sign a power of attorney authorizing someone else to take care of any matters the spouse could personally do, as long as they mentally competent, regardless of whether they are incarcerated or not.  A spouse does not have "a right to everything" if the other spouse is incarcerated.  Spouses often own community property which is subject to their joint control.  A spouse signing a power of attorney does not negate the other spouse's rights with respect to joint management community property.  Spouses often also own property that is one spouse's separate property or is the sole management community property of one spouse.  A power of attorney signed by a spouse can give the attorney-in-fact named in the POA the authority to control the separate property and the sole management community property of the spouse that signed the POA.