Late last month, Fraser Anning from Katter's Australian Party argued in the Senate that people must have the right to self-defence following a recent spate of what he called "horrific violent crimes against women".

He called on the Federal Government to allow the importation of pepper spray and encourage the states to legalise carrying it, saying it provides a non-lethal and easy-to-use means of protection.

His motion failed 46-5, with only David Leyonhjelm (Liberal Democrats), Cory Bernardi (Australian Conservatives), Peter Georgiou (One Nation) and Brian Burston (United Australia Party) adding their support.

Most of the subsequent attention has been on the comments about Greens senator Sarah Hanson-Young made by Senator Leyonhjelm during that debate.

But there's a fact about pepper spray that may have escaped your attention. While it's illegal to bring it into Australia, with import permits only issued for police or government use, the laws about carrying pepper spray for self-defence are different around the country.

Lorraine Finlay, a lecturer at the Murdoch University School of Law in Perth, says the one place where it's legal to carry pepper spray for self-defence is Western Australia. But you'll want to keep reading before going out and buying it.

First, just to clarify — we're talking about the same substance used by police

Pepper spray comes in the form of an aerosol. It's used to incapacitate people by causing temporary blindness, difficulty breathing and a burning sensation on the skin.

The side effects usually last for less than an hour. A report by the Queensland Crime and Misconduct Commission into its use by police found pepper spray was "relatively safe", but does cause intense pain.

The spray itself is made with "oleoresin capsicum", which comes from chilli peppers. That's why it's sometimes called OC spray. (And in case you're wondering, Mace is a specific brand that makes pepper spray, though that term is often used to refer to any type of defence spray.)

A police officer holds a can of pepper spray at a protest in Seattle in 2016. ( Flickr: Adam Cohn )

Each of the states have different laws about pepper spray, but they (almost) all have the same effect

The difference in WA is that pepper spray is a 'controlled weapon'

That puts it alongside things like crossbows, spear guns or swords which can also be used in the state if you've got a "lawful excuse" — for instance, if it's used in martial arts.

This is the lawful excuse for having pepper spray:

"If it is carried or possessed by a person for the purpose of being used in lawful defence in circumstances that the person has reasonable grounds to apprehend may arise."

That still means not everyone can just start carrying pepper spray for self-defence.

Proving that you have reasonable grounds is where things get complicated

Ms Finlay says we do have a sense of what the law means.

"For example, one of the Supreme Court judgments mentioned if you were a woman walking home alone at night after work, you may well have reasonable grounds for carrying pepper spray," she said.

The elderly or vulnerable people might also be in that category.

"But, for example, a regular person in broad daylight who's never had any history of an assault or that type of thing happening to them would have no reason to need to carry pepper spray," Ms Finlay said.

If you're wondering where exactly the line is, you're not the only one

Ms Finlay says nobody really knows where they stand. That's because you can't know for sure if you've got "reasonable grounds" until it's been tested in court.

"That's the really tricky thing about the law in Western Australia," she said.

"It's actually quite unclear — firstly because you don't know if the defence will hold up in court, and obviously different judges can have different views.

Ms Finlay says the other problem with the law is that people don't always know in advance if they're going to need pepper spray.

"There are times when things happen out of the blue," she said.

Ms Finlay says the law needs to be clarified, and it's up to WA's Parliament

Pepper spray maker Sabre has the tagline "Making Grown Men Cry Since 1975"

She says it makes sense to have very clear rules so that people who have the right to carry pepper spray in self-defence know that they have that right.

"And if it's not going to be allowed, then again those rules need to be clear so that people don't unintentionally find themselves on the wrong side of the law," she said.

But there's varying opinions on whether pepper spray should be able to be carried for self-defence.



Another expert says legalising pepper spray for self-defence isn't a good idea

Adelaide Law School's Kellie Toole, an expert in laws surrounding self-defence, says pepper spray poses a similar dilemma to that of gun laws in America.

"Items that are maintained for self-defence can actually have the perverse effect of creating risks for the users and other members of the community, through accidental or deliberate misuse," she said.

"While I am very sympathetic to the right of women to feel safe, I agree that it should be prohibited for reasons of public safety."

Ms Toole also questioned the motive behind the push for the legalisation of pepper spray.

"I do think where certain men are suddenly advocating for women's rights and women's safety there is the possibility of an alternative agenda, and victim safety can easily blur into a vigilante mentality of which gun laws can be a part," she said.

Ms Finlay agrees we don't want to go down America's path

She noted the concern was that "if you open the door to one type of force being able to be used, then you gradually open the door to other forms of force".

Ms Finlay said she hoped no-one would ever use women's safety as a "ploy for anything else".

But she also said that while we don't want community members carrying weapons "as a general rule", and noted the fear that pepper spray could get into the wrong hands, she said it nevertheless may be appropriate for some people to be able to carry it.

"This is a non-lethal item that could be used to protect people," she said.

"It does seem to make sense to me to allow people who are vulnerable and who perhaps do need to be able to protect themselves to have that peace of mind and security of knowing that they can do that."

However, both experts agreed the main issue is preventing crime.