Here’s an unusual non-tariff barrier from a 2006 WTO complaint brought by Panama (mentioned in Eaton, Jinkins, Tybout, Xu):

Second, Panama considers that, through three specific resolutions, Colombia has established a requirement that all goods falling under Chapters 50 to 64 of Colombia’s Customs Tariff (textile and footwear products) that originate in, and/or are imported from, Panama or China shall enter into Colombia only through specified ports of entry. This restriction on the ports of entry applies only to relevant goods coming from Panama or China and not to goods imported directly from third countries or customs territories. Panama claims that the restriction on the ports of entry appears to be inconsistent with Colombia’s obligations under Articles I:1, V:6, XI:1 and XIII:1 of the GATT 1994.

Third, Panama considers that, through a specific resolution, Colombia has established a requirement that commercial invoices of goods coming from the Free Zone of Colon shall include, in addition to the regular requirements, the name of the buyer in Colombia, his address and his Tax Identification Number (“NIT”). This requirement applies only to goods coming from the Free Zone of Colon and not to goods originating in third countries or customs territories. Panama claims that this requirement appears to be inconsistent with Colombia’s obligations under Articles I:1, V:6, XI:1 and XIII:1 of the GATT 1994.

While Panama and Colomiba reached a mutual agreement to solve these issues in December 2006, a closely related July 2007 complaint revisited exports from the Free Zone of Colon, which again faced port-of-entry restrictions:

In relation to restrictions on ports of entry, Panama’s request for consultations is directed at a resolution of June 2007 which provides that all goods classifiable in Chapters 50-64 of the Customs Tariff coming from the Free Zone of Colon in Panama shall be entered and imported exclusively through the jurisdictions of the Special Customs Administration of Bogota and the Barranquilla Customs Office. This requirement does not apply to goods arriving directly from third countries. The regulation provides that with respect to these goods, the authorization of the customs transit procedure will not be appropriate. Furthermore, the import declaration applicable to these imports shall be presented prior to their arrival in the national customs territory but not more than 15 days in advance. If an importer does not comply with these requirements, it is subject to special procedures under Colombia’s Customs Code, including the detention of goods.

Panama considers that these restrictions are inconsistent with Colombia’s obligations pursuant to Articles XI:1, XIII:1, V:2, V:6 and I:1 of the GATT 1994.

Colombia lost this WTO case and conformed to the DSB’s ruling in 2010.