Washington State is no different from other states in that it allows the government to seize property based only upon probable cause that the property is connected or derived from felony activity such as drug trafficking. Some states even allow seizure and forfeiture of vehicles driven by people under the influence of drugs or alcohol. RCW 46.61.5058.
Laws such as these are extremely unfair because they deprive people of their property without due process of law. The due process only comes after the government has taken the property.
However, there are challenges that can be made to the seizure and forfeiture. Just as there are challenges to arrest, so are there challenges to seizure and forfeiture. The Fourth Amendment to the United States Constitution applies in forfeiture hearings. So if the government agents acted without probable cause or without a warrant, the property seized will be returned to its rightful owner.
Perhaps even more important than the Constitutional arguments are the procedural arguments. Often attorneys for the government make mistakes in the way they handle these cases especially with regard to the all important timelines.
For example, I have had several cases where the police have had to return the seized property because they missed the deadline for the hearing. This is always extremely gratifying to my clients.