If he has no intent to return to CA he definitely should obtain a DC drivers license and he should register to vote in DC.
To access CA Form 540NR, go to the personal info section of TT and enter his State of Residence as DC, and indicate that he had Other State Income from CA. This will prompt the program to produce the 540NR. When you do the 540NR, allocate zero income to CA.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
