They don't want you to fish for Coho because you might catch a king! NOT KEEP ONE! you might hook one and release it.
Now if you want to buy one and eat one now that is ok... just go on Craigslist...Puget Sound King Salmon for sale...

I have both Smoked and Fresh Frozen Alaskan Sockeye Salmon and a limited supply of Fresh Frozen Puget Sound King Salmon.
King Fillets: $14/lb. (packaged in 3/4lb. servings)

http://seattle.craigslist.org/tac/fod/5267687837.html

I sure am glad the WDFW is protecting our resource from accidentally hooking one on a single barbless hook "the most deadly form of fishing"

"Closure to salmon fishing until further notice is needed to protect Endangered Species Act-listed sublegal chinook salmon that are being encountered incidentally by anglers at a higher rate than expected".