Washington MM Laws Regarding Guns and Employment

I am looking for two scenarios:

A.) When going to the gun range or carrying a legal concealed pistol, how does a MM Permit compare to laws regarding Guns and Marijuana charges. For example: One who uses MM at night to alleviate chronic back pains, but by day is not under the influence.

B.) An employer requests a pre-employment drug screen. The applicant is a MM user (licensed). How does the permit protect said applicant? Should applicant disclose use and permit status to employer prior to agreeing to take the screen?

I am looking for any legal references, pro or con, that I can refer to. Any attorneys who I can contact for more specific legal statutes?

Thanks.