Pepper spray is a 'prohibited weapon' in Victoria and you can not have it all.
Crimes Act 1958 - Sect 462A
Use of force to prevent the commission of an indictable offence
A person may use such force not disproportionate to the objective as he believes on reasonable grounds to be necessary to prevent the commission, continuance or completion of an indictable offence or to effect or assist in effecting the lawful arrest of a person committing or suspected of committing any offence.
At common law, the leading case on self-defence is Zecevic v DPP (1987) 162 CLR 645
The majority of the High Court said at 661:
The question to be asked in the end is quite simple. It is whether the accused believed upon reasonable grounds that it was necessary in self-defence to do what he did. If he had that belief and there were reasonable grounds for it, or if the jury is left in reasonable doubt about the matter, then he is entitled to an acquittal. Stated in this form, the question is one of general application and is not limited to cases of homicide.