A Thought Experiment about Illegal Immigration

There is a very good article here in a blog called Practical Ethics which asks if there is a moral/ethical basis for treating our fellow-citizens better than foreigners.  This is a very relevant question since those who answer in the affirmative seek to give priority to citizens over non-citizens for public goods and services or in some cases to actually deny such things to foreigners because they are not "us.".  This is what Marine Le Pen is arguing when she calls for French citizens to be first in line for such things as public housing.  As a foreigner I think you can probably guess where I come down in this debate.

But the article inspired me to think about other ways that we express our partiality for our compatriots and how we might behave when we meet our fellow citizens outside of our national territory.  Here is my own thought experiment:

At home your political views are clear.  You are a supporter of immigration but only legal immigration.  You feel it is unfair to citizens and legal residents alike when workers enter your country illegally to work and use social services.  You think it is only fair that such people be deported since they are breaking the law. 

Then one day, you are traveling in foreign land and you are delighted to meet some of your compatriots who live in that country full-time.  Over a few beers, you are expressing your admiration for their ability to integrate (their language skills, local knowledge and so on) when one of them admits that he overstayed his visa/student permit long ago and is essentially living in the country illegally and working under the table. 

Given how you feel about illegal immigration in your home country, does it make a difference to you when it is one of your own people doing exactly the same thing in a foreign country?    Would you denounce your fellow citizen to the local authorities or would you ignore it?  And what would be your rationale for acting or not acting? (And please don't tell me that you couldn't do anything because don't speak the language or know how to contact the local police in a foreign place - if your wallet were stolen, you wouldn't hesitate).

Think about it.