This morning I lookup the law govern cannabis usage in Australia, because I am interested in growing one for personal use. Found the following info from NCPIC detailing variation in each state:

ACT - Possession of up to 25 grams or 1 plant, is not a criminal offence but carries a $100 fine.

NSW - Possession is criminal, but with less than 15 grams, offenders can receive up to two cautions.

VIC - Possession is criminal, but with less than 50 grams, offenders can receive up to two cautions.

QLD - Possession is criminal, but with less than 50 grams, offenders can receive only one caution.

WA - Government plans to decriminalise possession of up to 30 grams or one plant, but $200 fines will apply. First-time offenders are now cautioned.

SA - Possession by adults of not more than 100 grams is not criminal but carries fines of up to $150.

NT - Possession by adults of up to 50 grams or 1 plant is not criminal, but carries a fine of $100.

TAS - Possession is criminal, but offenders with less than 50 grams may be cautioned.