Not true. Law-makers never intend the law to be ambiguous. In fact, it makes the jobs of the court much harder since the interpretation of courts constitutes a precedence and guides the future decisions of the courts.
In fact the criticism of ECPA is that it is a very vague law and that is precisely why the court is struggling with the interpreting it.
I would argue that there's a subtle difference between being ambiguous and being vague. Being vague implies that the intended meaning cannot be discerned, while being ambiguous implies that the law can be interpreted and applied to multiple scenarios, even those that did not exist at the time of its writing.
IANAL nor have I read the ECPA itself, but from my understanding of the case, the judge fully understood the intention of the law and applied it appropriately to this case. Had the law been less ambiguous and more specifically defined "radio technologies," then we may have ended up with a situation where wiretapping encrypted wifi might actually be considered legal. See mattmanser's explanation above (http://news.ycombinator.com/item?id=2721831)
Of course, there is a fine line between being too vague and being too specific.
In fact the criticism of ECPA is that it is a very vague law and that is precisely why the court is struggling with the interpreting it.