The law required that plaintiffs submit a "Certificate of Merit" along with any suit alleging medical malpractice. The "Certificate of Merit" is a document that must be signed by a medical professional with expertise in the defendant's field. By signing the Certificate that doctor is basically saying that he feels there is a probability that the standard of care was violated. In order for malpractice to occur the standard of care has to be violated, then that violation has to be the cause of the injury.
The court opined that requiring plaintiffs to produce evidence before discovery (the period during which the two sides trade documents and information) placed an undue burden on the plaintiff. The court also determined that the requirement passed by the legislation interfered too much with the judicial branch and access to the courts thus it was unconstitutional.
With politicians all over the place talking about "tort reform" it's important to realize that what they're really talking about is taking away rights of the patient. As if the medical malpractice deck wasn't stacked high enough already. At least now it's one card lower, but only in Washington.