The bloc's full members are Argentina, Brazil, Paraguay and Uruguay, with Venezuela's membership yet to be ratified; Chile, Bolivia, Colombia, Ecuador and Peru are associate members.  Until now, Mercosur has been marked by divisions more often than by consensus, in particular over the failure to do away with intra-bloc barriers to free trade and the complaints of the two smallest members that Mercosur business is decided bilaterally between Argentina and Brazil, which between them account for some 95% of the existing bloc's GDP.  Both Uruguay and Paraguay have been considering bilateral trade deals with the United States, which could raise questions over the institution's continuity.

On this occasion, however, members and associate members appear united in wrath over the recent EU adoption of the Return Directive harmonising European norms on illegal immigrants.  The measure will involve tougher terms for detention and expulsion of illegals -- and a five-year ban on their return -- for Latin American immigrants in Spain in particular (although, despite the widespread perception in the region, the Directive was not primarily aimed at Latin Americans).  Mercosur members and associate members have already issued a statement repudiating the 'discrimination' implied by the directive, as have a number of individual member governments, and Paraguay has promised to raise the issue at the summit in order to fix a common position. 

That position may imply the demise of -- already moribund -- talks on an association agreement between Mercosur and the EU.  However, disagreements on EU barriers to agricultural imports and agricultural subsidies, on the one hand, and Brazilian and Argentine objections to the opening of access for services and manufactures, as well as the question of rules on government procurement, on the other, already appear to represent insurmountable obstacles.  As such, the Return Directive may prove to be a convenient argument for ending an unsuccessful process, as well as allowing for a rare moment of harmony among Mercosur members themselves.