MGM vs Grokster

Someone has to explain to me the recent decisions by the Supreme Court. The highest court in the land is where we turn to for clarification when there is ambiguity in the law but instead the court has recently issued decisions that does exactly the opposite. The court's recent decision on MGM vs. Grokster not only seems to confuse the issue but also puts a legal warning against innovation. Anyone is welcomed to innovate but they won't know whether they have actually broken the law until someone sues them and the law pretty much says that anyone can and should sue. How can the justices claim their ruling was meant to protect innovations through a test that doesn't even clearly define what passes and what doesn't other then to go through a trial?