The stimulant, said by the IRB, to have "effects said to be less than amphetamine and ephedrine and slightly stronger than caffeine'', is only prohibited while players are in competition.
Tew said Gould's suspension was an important lesson for players in New Zealand. The majority of professional players take supplements.
"They must take care as the consequences for their playing career can be severe,'' he said.
Tew said 1720 tests had been carried out in New Zealand over the past five years and there had been only two minor violations.
Gould played the tournament as part of the women's sevens talent identification programme. Her suspension is backdated and ends in January, 2015.
Tew said no other positive cases were pending.