In Australia nicotine is classified as a “Schedule 7” substance by the Federal Poisons Act, which prohibits it’s retail sale in any concentration.
The good news is that nicotine for personal use is covered by the Personal Importation Scheme, Customs – The only restriction is that nicotine is imported for personal use and not for resale.
The TGA will state that you may only import up to 3 months supply but the TGA DO NOT have jurisdiction over ecig parts or the liquid as long as the manufacturers do not make therapeutic claims. Nicotine is not a medicine, it does not treat or cure any diseases, so, The TGA can butt-out!
Check your state or territory laws for rules regarding possession of Nicotine.