Thats defenently right SpiritWarrior, and there are a lot of laws out there, say your a kid driving after a curfew you didn't know about, and you get pulled over. I'm sure the officer would prolly just let u off with a warning if he was nice enough, but they wouldn't take ignorance as an excuse.

Ignorance of the law is no excuse, but specific criminal laws have what is know as mens rea requirements, literally a 'guilty mind' i.e. some kind of mental element to the offence, which can range from direct intent through to strict liability, where merely doing the act is enough.

Thus, with the drugs example, if the offence was to smuggle drugs with the intent to do so you would have to prove this intention to be guilty. But intentionally smuggling drugs in ignorance of the law would still be an offence.

With the 911 things its probably strict liability, therefore ringing 911 without good cause would be enough to be guilty, but if it were ringing 911 with the intention to waste their time she wouldn't be guilty, as she didn't want to waste their time, she genuinely thought that was a service they provided.

So, it depends on the wording of the actual law in question.