The 28-year-old man accused of the Christchurch massacre has been denied the right to have visitors and has no access to newspapers, radio or television.
He has been segregated from other prisoners and is able to be observed 24 hours a day, either directly by staff and/or via CCTV camera.
Gallavin said he was sure the complaint would trigger disgust in most New Zealanders but all prisoners have those entitlements.
"We show them dignity and respect that each in their own may have not shown to their victims - but that's the price we pay for being a principled society."
He said New Zealand had an incredibly rare opportunity to try a person in this situation.
People accused of such crimes were normally dead because they have killed themself or have been killed by somebody else.
"We need to be giving him an absolute fair trial and wherever possible this needs to be as open and not hidden as possible."
Gallavin said that included giving the man the entitlements under legislation.
Criminal Bar Association president Len Anderson told The Weekend Collective that while prisoners do have rights, they aren't black and white.
"While prisoners are entitled to visitors, the visitors have to be approved and be suitable people. And similarly, while they are entitled to make phone calls, they have an unlimited right to make calls to legal advisers, but outside of that there is some control over it."
However, Anderson also stressed prisoners do have rights and they are enforceable.
If an investigation finds the Department of Corrections does not have secure ground to limit the alleged gunman's entitlement then those rights will be reinstated.
Gallavin said it was unlikely the accused man would get compensation for the breach.
"I think we are in for a rough ride in New Zealand. This person, I suspect, is going to try to defend himself from start to finish and he's going to be meticulous upon rights."
