He had been a sporting administrator for 17 years.
"Over that time, I can assure you that our volunteer numbers are falling and it's my view that a lot of that has to do with over-compliance and the fear of enforcement linked to being liable.
"They are all small players but they are significant in the bigger sport and recreation wheel."
The act allows for penalties of up to $300,0000 on individuals running PCBUs who fail to meet their obligations to provide a safe workplace.
Cooper said there were 7500 not-for-profit organisations which employed one to five staff.
"This is the issue at the moment which is creating a real concern for us because it is diminishing. We feel as though the volunteer numbers are declining.
"There's too many rules and we are losing that important I suppose crown jewel of New Zealand and that is the volunteer base."
Asked later how he felt about his debut before a select committee, he said he was probably equally nervous about the appearance as he was in his first test.
"A good environment and it's one of those other experiences in life that you do."