He even suggested people with foreign-sounding surnames would have to jump through hoops.
While there is some merit in the argument that the ban is solving a non-existent or fading problem, it has nonetheless been Labour policy since July 2015 to find a way to ban sales of existing houses to non-resident foreigners that was consistent with the Trans Pacific Partnership before it could support the deal.
It was asking too much of National to negotiate such an explicit clause in TPP for a future government.
Free trade agreements are liberalising documents and the caveats tend to be around retaining existing powers, rather than preserving the right of future governments to reverse existing liberalisation.
Among the exceptions negotiated in TPP, it retained the right of a New Zealand government to impose "any tax measure" on the sale of residential property, which National argued could be used by Labour.
It also retained the right to change criteria under the Overseas Investment Act - and Labour is going to use that right in order to effect a ban on foreign speculators.
Residential housing will come within the definition of sensitive land which requires permission, if bought by foreigners, and which won't be granted under new criteria.
Both options were available and Labour has chosen one.
The Government will move swiftly to change the law before the TPP enters into force.
But the existing reservation in TPP to change the Overseas Investment Act suggests there would be sufficient safeguards for it to do so afterwards as well.
New Zealand TPP officials in Japan are arguing the new Government's case to ditch the Investor-State Dispute Settlement clauses of TPP - but that is not a battle the government expects to win and it certainly won't ditch TPP over its failure to do so.
It will be able to say it tried but failed on ISDS, but a successful TPP is the more likely outcome.
