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.