Depending on the facts of your case, a signed waiver or release of liability may or may not be enforceable. We have all signed agreements that had "release of liability" clauses in them such as when you join a gym, rent roller skates, or buy a ski lift ticket. These agreements are legal contracts and if enforced in Court, may be used as a complete defense barring any recovery from the protected person or legal entity. However, there is Washington case)law that helps injured parties get around such releases or waivers by invalidating the exculpatory clauses of the contract or waiver.
The general rule in Washington is that a liability waiver is enforceable unless: 1) it violates public policy; 2) the negligent act falls greatly below the standard for protection of others; or 3) the waiver is inconspicuous. Johnson vs. Ubar LLC., 150 Wn. App. 533, 537-538 (2009). Of course, these exceptions must be viewed through the individual facts of each case. There is extensive, well-developed case law which sets forth factors to be considered when making arguments to exclude a liability waiver.
Under the "violates public policy" argument, the following cases should be consulted: Shields vs. Sta-Fit, Inc., 79 Wn. App. 584 (1995); Wagenblast vs. Odessa School District, 110 Wn. 2d 845 (1988); and Chauvlier v. Booth Creek Ski Holdings, Inc., 109 Wn. App. 334 (2001).
Under the "falls greatly below the legal standard" argument, McCutcheon vs. United Homes Corp., 79 Wn. 2d 443 (1971) is the place to start.
Under the "inconspicuous waiver" argument, the starting point is Baker vs. City of Seattle, 79 Wn. 2d 198 (1971).