Doesn't the new rule require you to have a CPL, and the pistol be concealed?
Yes!
Hunting equipment: Hunters using muzzleloaders or archery equipment will be allowed to carry a handgun for personal protection if they have a concealed pistol permit. Hunters may also use black powder pistols to hunt during muzzleloader seasons.
Their reasoning is:
The commission has always been concerned about the potential for individual bowhunters to use a sidearm to unlawfully kill big game. Knowing that individuals with concealed pistol licenses (CPL) are thoroughly vetted through a criminal background history check, the commission has a high level of confidence that CPL holders will not wish to jeopardize their license. There is no such assurance with the general hunter who does not possess a CPL.
The above is from the thread here by Machias:Got a response from the WDFW concerning CWP
http://hunting-washington.com/smf/index.php/topic,24881.0.html