[pmccool]

That depends on whether you're talking about statute or common law. With statute law, no law does mean "not prohibited". With case law it does not: the courts can and do make up new law to fit the facts.

Lack of case law affords no protection. It just makes it hard to predict the outcome in advance.

[Gormo]

Well, if there are no statutes nor established case law precedents that apply to or can be extended to a particular situation, any cases would be more a matter of equity than law. And neither common law nor equity rulings apply a priori; a case must be brought to the court after the fact in order for the court to make a ruling on it. Common law also requires mens rea for any action to be considered an offense.

So even in a situation where a court would award damages if a case was filed and malicious or negligent harm were proved, I'm not really sure it makes sense to say that anything was "prohibited" in advance.

[pmccool]

Not prohibited != can be done without legal consequence.

New torts are invented, albeit rarely. Every so often there's a new duty of care in negligence. There are, I'm sure, other examples and the point is this: the lack of case law wasn't much help to the first defendant to lose on that point.