Legal Question in Family Law in Washington

That's a "yes and no" answer. Theoretically, if his 401(k) was earned during the marriage and prior to the date of separation, then it is community property and you own half of it. However, as a practical matter, unless there are court orders in place, even at least a temporary order barring him from touching the money without your approval or that of the court, then as a practical matter, he is pretty much free to do as he wishes.

If you are separated and intending on divorcing, you should look to hire local counsel as soon as you can to try and put in place temporary order pending a finalization of your dissolution of marriage (divorce) and then ultimately enter what is known as a qualified domestic relations order, which is the vehicle by which we divide 401(k) accounts so that you get your fair share when your fair share.