"Venues have a legal responsibility to look after their gambling patrons, just like they do when serving alcohol," Thornborough said.
"Gambling operators and staff involved in gambling all have the policies, procedures, and training they need to identify and manage problem gamblers. There is no excuse for failing to identify problem gamblers."
Thornborough said this prosecution signalled the regulators focus on cracking down on venues failing to meet their obligations.
"As New Zealand's gambling regulator, we support the gambling sector to address the harm of gambling. However, we will not back away from prosecuting in cases where we have evidence to suggest that staff in gambling venues have failed to take all of the reasonable steps necessary to identify and look after problem gamblers," he said.
"We will not stand by and watch as venues ignore patrons showing signs of problem gambling."
DIA would not comment further or provide details as the case was before the courts.
The 2003 Gambling Act requires employees of gambline venues to take reasonable steps to ensure effort is being made to "identify actual or potential problem gamblers".
DIA said it regularly carries out audits and "mystery shoppers" to test whether venues' harm practices are working.