Jeff Even wrote:

We issued a formal opinion on a similar question after the
1990 Census.  I'm
attaching a link, but in case it doesn't work the citation
is 1992 Op. Atty
Gen No. 12 (Wash. 1992).

http://www.wa.gov/ago/opinions/1992/opinion_1992_012.html

Jeff Even
Assistant Attorney General
Solicitor General's Team
PO Box 40100
Olympia, WA 98504-0100
voice: (360) 586-0728
fax: (360) 664-2963
jeffe@atg.wa.gov