Patrick Harvie has insisted the Scottish Government policy of freezing rents across the country for the next six months will withstand any legal challenge.
A coalition of landlords last week announced it was considering using the courts to get the emergency legislation thrown out.
Harvie, the minister for tenants' rights, played a key role in guiding the bill through Holyrood - and insisted it was needed to help the many Scots who were struggling with the cost of living.
The Greens co-leader told the Record there was a "decent level of protection" for landlords who may be experiencing financial hardship.
"We believe the legislation is robust and legal, he said. "This question hinges on ECHR compatibility - and we believe it is compatible and it is legally competent."
Harvie was speaking before the Scottish Greens meet in Dundee this weekend for the party's annual conference.
Asked if he was disappointed that landlords were considering action, Harvie said: "I am, to be honest.
"Clearly, there are landlords in different financial circumstances and that's why there is a package of safeguards for those who may be facing hardship at the moment.
"There are landlords who are very responsible and landlords who are more exploitative.
"Remember, this doesn't stop them having rental income, they just can't increase it during a cost of living crisis for six months.
"That's a decent level of protection for tenants and it's balanced with safeguards for landlords facing hardship.
"It's an important step in protecting people from an unprecedented cost of living crisis made worse by the UK Government's reckless financial mismanagement."
MSPs voted in favour of legislation last week after an emergency procedure meant it was passed in just three days.
The move was backed by Nicola Sturgeon as way of helping Scots who are struggling with the cost of living.
The legislation will cap rent rises at zero per cent until March 31 - but SNP and Green ministers could extend the legislation for two six-month periods.
A group of landlords and letting agents has now announced plans to seek a legal opinion on the legislation, assessing if it breaches the human rights of landlords.
The coalition – which includes the Scottish Association of Landlords (SAL), Propertymark, the National Residential Landlords Association (NRLA) and Scottish Land and Estates (SLE) – has instructed Lord Davidson KC to deliver an opinion.
John Blackwood, chief executive of the SAL, said the action is being taken "with a heavy heart".
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