Businesses will still have the final say over their drug policies regardless of whether cannabis is legalised, according to an employment expert.

Kiwis will get their chance to vote on whether to legalise cannabis at next year's election. Yesterday, the Government revealed details of the upcoming referendum which is set to be a simple yes/no question.

Buddle Findlay senior associate, Shaun Brookes, told Mike Hosking employers would still be able to make their own rules around being intoxicated in the workplace regardless of the vote's outcome.

"Employers should still expect their employees to turn up to work [and be] able to do their roles. They shouldn't be impaired by alcohol, cannabis, or any other drug which could lower their reaction time, impair their decision making or make them less productive."

However, he said there are questions over whether an employee could smoke cannabis at work events like Christmas parties.

"Some guidance from the employer as to what their expectations for their employees are, prior to the Christmas party would be helpful."

"We can see in America, in some of the states where cannabis has been legalised, some employers still have a zero tolerance policy for cannabis for their employees."

He said while most New Zealand employers probably won't take a zero-tolerance approach, some in safety-sensitive industries might.

Brookes said drug use is already an issue for a number of workplaces and they will already have policies in place which won't need to be changed much.

"Their policies and their individual employment agreements should cope with and they should be in place at the moment. I don't think there will need too much in the way of amendments should cannabis be legalised," he said.

The referendum at the 2020 election will ask about support for a bill that details a regulated legal market.

It will include:

• Allowing products to be bought only in a licensed premise from a licenced and registered retailer
• A ban on using cannabis publicly, allowing it only in a special licensed premise or on private property
• Rules around private home-grown products
• A ban on advertising of cannabis products
• A legal purchase age will be 20
• A public education programme
• Stakeholder engagement