The RCW pertaining to illegal posting that was repealed in June 2012 was 77.15.220. It read as follows:
(1) A person is guilty of unlawful posting if the individual posts signs preventing hunting or fishing on any land not owned or leased by the individual, or without the permission of the person who owns, leases, or controls the land posted.
(2) Unlawful posting is a misdemeanor.
As for "accidentally" drifting onto private land: if the land is posted, fenced, or not apparently unimproved and unused, then you can be cited for trespass. Conversely, RCW 9A.52.010 states that “A person who enters or remains upon unimproved and apparently unused land, which is neither fenced nor otherwise enclosed in a manner designed to exclude intruders, does so with license and privilege unless notice against trespass is personally communicated to him or her by the owner of the land or some other authorized person, or unless notice is given by posting in a conspicuous manner.”
As of June 2012 there is a new provision pertaining to trespass that applies to hunters: RCW 77.15.435. This law allows a hunter to access private land to retrieve wildlife under certain conditions. The hunter may claim a defense against trespass if “The actor, after making all reasonable attempts to contact the owner of the premises, retrieved the hunted wildlife for the sole purpose of avoiding a violation of the prohibition on the waste of fish and wildlife as provided in RCW 77.15.170. The defense in this subsection only applies to the retrieval of hunted wildlife and not to the actual act of hunting itself.”
