The Labour Party says it may defy the Trans Pacific Partnership's rules on property sales if it enters Government.
Finance spokesman Grant Robertson said his party wanted to reserve the right to legislate in the best interests of New Zealanders.
"We think it is in the best interests of New Zealanders to give all of us a fair go in buying our own home," he told Radio New Zealand.
"If that requires passing legislation to limit overseas buyers from purchasing land and housing then we want to be able to go ahead."
The Trans Pacific Partnership (TPP) includes a non-discrimination provision which would prevent the New Zealand Government banning foreign nations from buying property in New Zealand.
This provision went against of Labour's bottom lines for supporting the deal.
Mr Robertson said: "We will take a good look at the agreement and we are reserving the right to review and renegotiate.
"There is always the scope to review them, there are just consequences if we make a law, there are consequences if we go against the agreement.
"We will have to look into what all of those are and balance that up."
The TPP also includes provisions which allow investors to seek compensation from the Government if it breaches its investment obligations.
This meant if a Government banned foreign investment in housing it could face a legal challenge from overseas investors or companies.