No pretending to be an engineer can have deadly consequences. Imagine someone saying they're an engineer and being contracted to build a bridge or building. That could (and has) have disastrous consequences.
You can be an engineer without an engineering license. Safety-critical jobs usually require a professional engineering license, but there are a lot of engineering work which is not safety-critical.
When it comes to civil stuff (i.e. the safety critical thing people think of when they hear engineer - bridges, buildings, highways, flood protection...) you absolutely can't call yourself an engineer without professional accreditation in every jurisdiction I know.
Even then (buildings for example), I believe some of the work can be done by non-licensed engineers. Stuff like land surveying, some electrical, CAD/modelling work, design of plumbing, heating, etc. can be done without license. I know a few people that aren't licensed but work on condos as engineers. I'm guessing a lot of the stuff has to be reviewed/approved by a licensed engineer, but that could be 1 to 5 licensed:unlicensed for example.
An engineering graduate, or an engineer-in-training. You can call yourself an engineer once you have several years of experience, pass some exams on law and ethics and whatnot, and get a professional designation.
There's only one state in Australia that has mandatory registration of engineers. There are several more states that are currently starting up mandatory registration schemes, and of course the national professional bodies operate voluntary registration and accreditation schemes.
Now of course that doesn't mean that you can just start building bridges as a non-accredited engineer, I expect the courts would look unkindly on you in a negligence lawsuit if your company had engineers that couldn't demonstrate their professional qualifications and development.
This is seen as a problem and the professional bodies are pushing more states to adopt mandatory registration, so we'll see more of that in the next few years, but it's not like Australia is a land where bridges fall down weekly without mandatory registration.
I could at least pretend that might happen if there was only one kind of engineer. But someone that incompetent at hiring might also hire the wrong kind of engineer. The rule doesn't do anything to help.
A P.Eng. is professionally obligated to refuse work that they're not competent to perform. You can't hire the wrong kind of engineer, because the engineer knows if they're the right kind or not.
Just to expand, I've never heard of an engineer from the wrong field signing off on a document (e.g. an EE signing off on a structure), but here's a lesser example of unskilled practice and the corresponding disciplinary action: https://www.apega.ca/assets/PDFs/discipline-decisions/18-011...