Immigration Minister Iain Lees-Galloway was informed of Karel Sroubek's violent crimes in the Czech Republic and allowed him to stay in New Zealand anyway.
Mr Lees-Galloway over-rode that original decision today and ruled Sroubek could be deported once he was released from prison.
Sroubek was "liable for deportation" because his Czech convictions meant he should not have been allowed in New Zealand in the first place, he said.
However, the case file - revealed under the Official Information Act - showed the Minister was informed of those crimes before he made his original call.
"Mr Sroubek is also wanted by Czech authorities for service of 54 months' imprisonment in connection with an incident on 28 June 1999, in which he attacked and grievously injured two police officers and another incident on 4 October 1999, when he attacked a taxi driver," the case summary said.
"It is understood that Mr Sroubek was convicted on 12 February 2002 of disorderly conduct, damaging of another's property and attacking a law enforcement officer."
Mr Lees-Galloway said he was only asked to consider Sroubek's New Zealand convictions and didn't think to consider the rest.
"I didn't think of that," he told reporters. "It would be quite extraordinary to expect someone to think of all the other possible questions that might be asked.
"I don't know every single detail of the Immigration Act... I didn't look at that and say 'aha, he should be an excluded person'.
"That wasn't something I was considering at the time."
Asked whether officials should have specifically pointed out that Sroubek could be deported on those grounds, Mr Lees-Galloway said a review into the whole process would consider that.
Sroubek came to New Zealand under a false identity which is why his Czech convictions went unnoticed by Immigration NZ when it approved Sroubek's temporary and permanent residency visas.
Sroubek's lawyer Paul Wicks QC said his client was disappointed with the decision and planning on appealing the decision through the Immigration and Protection Tribunal.
Sroubek was also weighing up a judicial review, he said.