Try the BIA Police (Indian Affairs). I believe they have an office in one of the Federal Buildings in Seattle. If there is no listing for Seattle then Try Port Angeles.

Absent that call the Jefferson County Sheriff's Department in Port Townsend. The reservation cuts through Jefferson County and the Deputies are probably familiar with the carry firearm law on the reservation.
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"90% of Life is just showing up and doing the work". Tred Barta Sr.