'Bring your own' (BYO) alcohol is a popular choice for unlicensed restaurants. In most cases, customers can BYO with your consent. If you're a restaurateur or staff member, you should know your obligations and the requirements for BYO alcohol.
You and your staff have the right to refuse BYO at your restaurant. Customers should not BYO without your consent. Generally, there's no offence for bringing BYO to a restaurant, provided the customer is at least 18. However, for some types of licensed premises, including cafes, nightclubs and certain public events, it's an offence to bring alcohol onto the premises (or take it away).
You should contact your local council about any BYO requirements. Some councils may need to be notified about BYO and may endorse this on your food licence.