Nowadays, consular registration can only be made if the person concerned is a Portuguese national. In the past, this precondition was only partially required.
Source 2013-2014: Ministério dos Negócios Estrangeiros, Direção-Geral dos Assuntos Consulares e das Comunidades Portuguesas (DGACCP), Portugal. On each country page, in box A3, on the website of the Emigration Observatory. LINK DGACCP