O'Reilly said employers should focus on how they can keep workers safe within their own businesses.
"I don't think we should be discouraging people from travelling. I think businesses should be operating as normally as possible."
Employers could look at other ways to protect their businesses and workers, such as splitting up the workforce, testing and using masks, he said.
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One care home worker, who wished to remain anonymous, said her boss told the workforce all leave from February would be cancelled because of the move to the red-light system.
They also strongly recommended no one travel outside of their region, particularly to Auckland, because it's "very high risk", and if she was to travel they would not be able to find cover.
"They put a bit of fear in me, they told me if I was to go to Auckland there is a high chance I will come back with Omicron and pass it onto the elderly and if that happened, I would feel a lot of guilt about that, it really puts me off leaving.
The woman said her reasons for travel was to catch up with a few friends, who she has not seen in a long time.
"We're all double vaxxed at work, we're going to get our boosters, we thought that's what we needed to have some freedom and do more things".
There is no legal basis for an employer to stop a worker from travelling during the red light phase.
Lawyer Mai Chen, an expert in employment law, said care and caution was different from prohibition, strong discouragement or some implied threat that if they travelled outside the region, they would be disadvantaged.
"It would be hard for an employer to show that refusing leave is reasonable due to the Omicron threat. It would be difficult for an employer to legally justify visiting adverse consequences on an employee for going to a wedding or going on a holiday outside the region."
But she could understand why an employer might caution staff from doing so due to Omicron.
Under the Health and Safety at Work Act, an employer is required to ensure all workers are able to keep themselves safe from Covid-19 and that the workplace does not create risks for the health and safety of customers or clients.
"The fact that someone is getting in a plane or driving to some of these festivals or events we've been seeing happening around the country like SoundSplash, that may result in them being put at greater risk."
Chen said ultimately it came down to a risk assessment and whether what the employer says to an employee was reasonable given the context.
Business New Zealand chief executive Kirk Hope said it would be a good idea for a worker to approach their boss to understand the rationale behind their decision and work through the safety requirements.
"When businesses are doing this, our advice to them is to make sure they talk to staff regularly about the measures they're putting in place to help protect them so they understand why those things are in place."