Salespeople and doorknockers who ignore stickers could now face hefty fines and have sales deals torn up in court.
Consumer NZ said new laws taking effect today were a triumph over "pushy salespeople hounding householders to buy products they don't want or need".
Changes to the Fair Trading Act were the product of an eight-year campaign against pestering salespeople.
"You don't need a sticker to benefit from these new consumer protections," Consumer NZ added.
"If you tell a seller to stay away from your house, they must do as they're told for two years."
Consumers could also complain to the Commerce Commission if traders refused to leave, or ignored stickers.
Apart from imposing fines, courts could order the cancellation or variation of a sales agreement.
Courts could also order compensation if an uninvited seller ignored a sticker or a direction not to enter a property.
According to MBIE, door-to-door sales were known as uninvited direct sales under the Fair Trading Act.
Special rules protected consumers when traders sold consumer products or services over $100 for personal, domestic or household use.
Rules were also in place if sales were negotiated at a home or workplace, by phone, or if a trader was not invited.