'Naughty' Smith slapped with ban
Coach Steve Hansen said the player was seen by "entering a disabled toilet cubicle with a female friend" at the Christchurch airport the day after New Zealand's 41-13 Rugby Championship win over South Africa in Christchurch last month.
Hansen said Smith accepted his behaviour was not of All Blacks standard.
As a result Smith was not considered for selection for this weekend's return Test against the Springboks in Durban.
The scrumhalf has returned home to New Zealand.
"Clearly, Aaron is bitterly disappointed in his behaviour," Hansen said.
"He feels he has let the team down, but just as important, he feels bitterly disappointed in letting his family and his partner down."
The New Zealand Rugby Union said it was supporting the action taken by the All Blacks in standing Smith down from the team to play South Africa this weekend.
"This was really bad decision-making by Aaron, which reflects poorly on him, and on the team," NZRU Chief Executive Steve Tew said.
Smith will face a misconduct hearing on his return to New Zealand.
He has failed to meet the standards that New Zealand Rugby and the public expect of our players.
"We are taking action to improve the culture of our game and are about to embark on an independent review of respect and responsibility in our professional player environment," Tew added.
"We have drafted the terms of reference and are currently talking to prospective panel members. We will provide an update on this shortly."
Given the misconduct process, the NZRU said it is not appropriate to comment further at this time.