The arguments for ignoring illegal immigration are as well-known as the self-interested motives that drive it. Open-border advocates argue that in a globalized culture borders are becoming reactionary and artificial constructs. They should not interrupt more natural ebbs and flows of migrant populations.
More concretely an array of vested interests sees advantage in dismantling the border:
Employers in hospitality construction food processing and agriculture prefer hard-working low-wage immigrants whose social needs are often subsidized by the government and who are reluctant to organize for higher wages.
The Democratic Party welcomes in impoverished immigrants from Latin America and Mexico. It hopes to provide generous social welfare assistance and thereby shepherd new arrivals and their offspring into the salad bowl of victimization and identity politics and thereby change the electoral map of key states from red to blue.
La Raza activists see unchecked illegal immigration as useful in maintaining a large pool of unassimilated and poor foreign nationals who look to group leaders thereby ensuring the 
continuance of what has become an industry of ethnic activism and careerism.
Mexico which is now offering advice to illegal immigrants on how best to avoid U.S. federal immigration authorities has the most to gain by porous borders. It envisions the United States as a relief valve destination to export its own poor and desperate rather than to have them agitate and demand costly social services from Mexico City.
Mexico enjoys some $25 billion in annual remittances predicated on the unspoken assumption that its poor and hard-working expatriates can only afford to send such vast sums out of the United States through the magnanimity of the American social welfare system that helps subsidize families to free up hard-earned cash. Mexico has learned that its own expatriates are loyal proponents who romanticize Mexico the farther away and longer they are absent from it. Yet lost in this conundrum are the pernicious effects of illegal immigration on the idea of citizenship in a consensual society. In the Western constitutional tradition citizenship was based upon shared assumptions that were often codified in foundational constitutional documents. The first pillar of citizenship is the idea that the nation-state has the sole right to create and control its own borders. The duty of all Western constitutions dating back to those of the Greek city-states was to protect their own citizens within clearly defined and defensible borders. Without a finite space no
consensual society can make rules and laws for its own enhance and preserve commonalities of language and culture or raise a military to protect its own self-interest.
Borders are not normally artificial or post-colonial constructs but natural boundaries that usually arise to reflect common bonds of language culture habit and tradition. These ties are sometimes fragile and limited and cannot operate on universal terms; indeed they become attenuated when borders disappear and residents not only have little in common but lack the mechanisms or even the desire to assimilate and integrate their migrant populations.
When borders are fluid and unenforced it inevitably follows that assimilation and integration also become lax as society loses a sense of who or even where their residents are. And the idea that the Bill of Rights should apply to those beyond U.S. borders may be a noble sentiment but the practical effect of such utopianism is to open a Pandoras box of impossible enforcement affronts to foreign governments endless litigation and a diversion of resources away from protecting the rights of citizens at home.
Residency is also confused with citizenship but they are no more the same than are guests at a dinner party and the partys hosts who own the home.
A country reverts to tribalism unless immigrants enter it legally often based on the hosts determination of how easily and rapidly they can become citizens and the degree to which they can benefit their adopted country and embrace its customs language and habits.
The Balkans Rwanda and Iraq remind us that states without common citizen ties affinities rights and responsibilities become fragmented and violent as their diverse populations share no investment in the welfare of the commonwealth. What plagues contemporary Iraq and Syria is the lack of clearly defined
borders and often shifting and migrating populations that have no stake in the country of their 
residence resulting in competing tribes that vie for political control to aid their own and punish the Other.
In sum there are several reasons to put a stop to illegal immigration. But among the most important and to often forgotten is the insidious destruction of what it means to be a citizen.
Victor Davis Hanson is the Martin & Illie Anderson Senior Fellow at the Hoover Institution and author of A War Like No Other: How the Athenians & Spartans Fought the Peloponnesian War".
