High level discussions are being held about the legal status New Zealand troops will have, if they're sent to Iraq.

A decision on a role in the fight against ISIS will be decided at Monday's Cabinet meeting... but John Key says he won't send anyone in, unless he's confident of their legal authority.

Dr Jim Rolfe from Victoria University's Strategic Studies Centre says a Status of Forces Agreement would cover a whole range of points, from who's in charge of protecting troops, to whether New Zealanders would be able to use their weapons if they're under attack.

He says there's also the question of jurisdiction, should there be any action by our troops which might be considered illegal under Iraqi law.

"This becomes an issue in a war zone or in a defined war zone where civilians can be caught up in fighting.

"In practical terms, the Status of Forces Agreement has to be reached because without it they're left in a state of complete uncertainty as to who's responsible if something goes wrong."