Originally Posted by Eagleks
That's very state specific and on top of that.... you are talking bordering states, which then have another set of rules. Best to check a local FFL that can answer the question.
As far as the BATF is concerned, the rules for bordering states are the same as those for states on opposite coasts. The Federal contiguose state regulations were recinded over 20 years ago.
State laws may apply but I don't see anything in Washington laws that apply.