In a presentation to the National Assembly's trade and industry committee on Wednesday, Sacob representative Ken Warren said there was a possible "jurisdictional lacunae" in the agreement.
This could result in a multitude of possible bilateral agreements being signed by individual Sacu countries with intended Free Trade Agreement (FTA) partners such as the United States, in, for example, the spheres of investment and trade in services.
These limited bilateral agreements would produce obligations for Sacu member states over and above their commitments to the FTA as a Sacu unit.
"The conduct of business in the region would become so complex that it could negate the purpose of the customs union," Warren said.
The flexibility of the Sacu Agreement regarding future inclusion of annexures or amendments, which would accommodate issues of greater economic integration and common policy, also had to be properly assessed.
This was necessary to ensure, as far as possible, the duplication of agreements and the regulatory system underpinning them, was avoided.
The speed with which such amendments could be brought was also important, as the proposed Sacu/US FTA was to be concluded by the end of next year, he said.
The committee was holding hearings on the proposed ratification of the Sacu Agreement, signed in October last year.