"For privacy and legal reasons, as is standard practice for all administrations, I can't disclose the details of this case. I can assure the public that this was a decision taken in full view of the information presented to me, and not a decision that I have made lightly.
"I will be making no further comment on this issue."
In the letter, Lees-Galloway notes that Sroubek is liable for deportation because he came to New Zealand under a false identity, and also because he was convicted of importing ecstasy.
The letter says that despite this, Sroubek will be granted a resident's visa as long as he provides a valid travel document in his true identity within five months.
The conditions of the visa include: that he is not convicted, in New Zealand or elsewhere, of any offence for the next five years, starting from his release from prison; that he not use any fraudulent identity in the next five years; that he not supply any false or misleading information to a Government agency for the next five years.
"This is a very serious matter and I do not condone your behaviour," Lees-Galloway says in the letter.
"I have given you one final chance to remain in New Zealand and this should serve as a clear warning to you .. I trust you will use this opportunity to make a positive contribution to New Zealand."
Lees-Galloway used his power of "absolute discretion" to cancel deportation liability and grant residence to Karel Sroubek, also known as Jan Antolik.
Absolute discretion decisions are often the last option available for people to remain in New Zealand for cases outside ordinary immigration settings.
National's immigration spokesman Michael Woodhouse, a former immigration minister, said Lees-Galloway had serious questions to answer.
"The information I have on this case does not come close to any threshold where special consideration should be given by the Minister," Woodhouse said.
"This Government has promised to clamp down on immigration, making it harder for Kiwi employers to fill skills shortages, yet it allows violent criminals to stay here."
Sroubek was jailed in 2016 for five years and nine months after being convicted of importing 5kg of MDMA with a street value of $375,000.
The conviction came four years after a judge discharged him without conviction despite being found guilty of having a false passport and lying to immigration officials.
He came to New Zealand from the Czech Republic in September 2003 to start a new life as Jan Antolik, after fleeing corrupt police who wanted him to lie and clear the main suspect in a murder investigation.
Instead, he left a videotaped witness statement which was later crucial in convicting the killer.
He fled the Czech Republic with a doctored passport but was unmasked in October 2009 when Czech police gave New Zealand police details of his identity and an arrest warrant on minor charges in connection with the 2003 murder.
Sroubek pleaded not guilty to the charges but admitted using a false identity to come to New Zealand.
His defence was he had a "reasonable excuse'' to give a false name as he had fled his homeland in fear of corrupt police officers and a criminal.
The Crown did not dispute his story but said Sroubek should have revealed his true identity to New Zealand authorities.
A jury convicted him in 2011 but Judge Roy Wade gave him a second chance, as a conviction would provide grounds for automatic deportation for the representative kickboxer.
He believed Sroubek would still be in danger from corrupt Czech authorities and the man he helped convict of murder if he were deported.
Four years later, Sroubek was convicted on the MDMA charge. He appealed against that conviction last year, saying the MDMA was planted to frame him.
The Court of Appeal rejected his appeal.
Sroubek has had other brushes with the law in New Zealand.
He was arrested in Operation Ark, a drug investigation, just days after his false passport trial in 2011.
He was later convicted of being a party to the manufacture of Class C drugs, although the conviction was later overturned on a technical ground.
Sroubek was also previously acquitted of committing an aggravated robbery with two members of the Hells Angels.
