Hospitality Ulster has said it is "seeking clarity" from the NI Executive about new coronavirus laws regulating the sector.
New laws took force on Wednesday as drink-only pubs were allowed to reopen.
One of the new rules is that no more than six people from two households can sit at a table inside a pub or restaurant.
It has emerged the regulations also now apply to people sitting outdoors at NI venues.
An amendment has been made meaning the rules regulating the hospitality sector, which originally only applied to indoor settings, now extend to outdoors venues.
The legislation was published by the Department of Health on Friday evening.
It states that the word "indoor" is omitted from the regulations, meaning the rules around table limits, music and dancing and contact tracing requirements also apply at outdoor venues.
Children under 12 are exempt from the number of people included in the table limit, and if a single household is bigger than six people, that is also permitted.
There are also more relaxed rules for table size limits at weddings, and a first dance is permitted for the bride and groom - but only to pre-recorded music.
Colin Neill, chief executive of Hospitality Ulster, said he appreciated the executive was "introducing laws at speed" to adapt to the changing situation, but that more detail needs to be provided.
"Making law fast has unintended consequences and lacks clarity," he said.
"It makes viability even more difficult for many of our members."
He said there were big questions around who enforces the laws, adding that his organisation is seeking clarity around the rules on music at wedding ceremonies.
Currently, the law states that live music is banned at hospitality venues, but it does not apply to places of worship.
Mr Neill questioned why the rules mean that singing or live music could be permitted at a wedding in a church - but not a hotel or other hospitality setting.
He said he hoped clarity could be provided quickly for both businesses and customers.
A spokesperson for the Executive Office said: "The regulations were amended to reflect the policy intent of the executive."