[rmnunez]

I disagree with the contention the Mexican government has ever encouraged its "undesirable" citizens to migrate consistently or not, there is no ethnic cleansing and certainly no evidence of an effort to get rid of poor economic or social performers. In the manual refered to before detailing how to cross safely, the aim is to save lives -not teach how to skirt restrictions. Though the Mexican government would be better advised to openly advocate disregard for US legal impediments to migration if they sought to advance any claims over the usurped territory, they really don't seek to advance those claims. The Mexican government is only recently genuinely representative, it didn't reflect the views of Mexicans in the past very well, so its failure to maintain and reiterate claims for the seized territory wouldn't conclusively show relinquishment if we could find a pattern of conduct among Mexican immigrants regarding the border (I think we can).

Since precolumbian times, long before the US even existed, Mexicans (before there was a Mexico either) crossed into what is now the US without any regard for the current border. I doubt this customary practice is premised on the average Mexican's belief some part of the US was wrongly seized from Mexico (though the idea does have some currency). Migrants from Mexico cross without passports mainly because they can't afford the paperwork, don't understand or simply don't know about passport requirements. However, the conduct is indistinct from what would be in evidence from someone who though well-aware of the border has chosen to disregard it.