Twisp River is correct. Only the Courts and HW can interpret the constitution.

With that said, the Sheriff certainly swore to uphold the constitution but what he swore to uphold was what the judiciary says it means. Not what he thinks it means. In Washington, if a local Sheriff started drafting memos about what the constitution means and then advised his officers on what they can and cannot do that would be unauthorized practice of law, a crime. In any event it looks like it was rightfully struck down.