Asked whether New Zealand had secured a Status of Forces agreement, Mr Brownlee said: "You can call it whatever you like."
He added: "I think all that you ever get is an agreement between two countries about the circumstances under which the soldiers from your country undertake the activities that they've designated to do inside the other person's country."
He confirmed New Zealand soldiers would have immunity in Iraq if they broke the law, as long as it was within the military mission.
A date for deployment had not yet been confirmed. Government has previously said it was likely to be at the end of May, though Australia's ABC News said the joint mission could take place as early as mid-April.
Mr Brownlee said New Zealand would head to the Middle East "when the conditions and circumstances were right".
New Zealand is sending 143 soldiers in total to help train Iraqi forces to combat the Islamic State, alongside 300 Australian troops.
Mr Brownlee said: "Where you've got to have inter-operability on a mission like this, it pays to have a little bit of time together as you go through the exercise of working out what that mission is going to look like."
The joint Australian and New Zealand mission will be based at Camp Taji, north of Baghdad.
Labour leader Andrew Little said he was surprised New Zealand troops had been sent to Australia because Prime Minister John Key said a deployment was unlikely until May.
"It does seem to the way that Government conducts itself on this issue. It just does what it likes and tells people afterwards.
"If our troops have been mobilised and left New Zealand we should have been told that. This is an issue that has split the nation and the Government in those circumstances has to be upfront."
Mr Little said that if New Zealand had not signed a Status of Forces agreement, which required ratification by Iraq's Government, then any legal protections could be insufficient.
