Sorry, missed this somehow: they are NOT issued for any legitimate diplomatic reason. They are issued so their citizens can illegally live in and get service in a foreign country.

They should never be accepted, by any institution, based upon the following FBI testimony to Congress in 2003:

http://www2.fbi.gov/congress/congres...craw062603.htm

This is the most worrisome, to me, from the testimony; quote: "Fourth, in some locations, when an individual seeking a Matricula Consular is unable to produce any documents whatsoever, he will still be issued a Matricula Consular by the Mexican consular official, if he fills out a questionnaire and satisfies the official that he is who he purports to be."

In other words, if you can lie fairly well, then you get a Matricula Consular Card.