It should be noted that at the same time the U.S. government is always obligated to protect the rights of U.S. citizens, it is NOT obligated to do any such thing for other nationals let alone for those who claim no nationality at all. For example, the matter of Elián González's immigration was one of deferring to sound philosophy whereupon he was to be united with his family in Florida. Given that there already existed _explicit_ laws on the books for automatically naturalizing Cuban political refugees, and given that migrating the rest of González's family to America would be of negligible cost to other Americans, there was no legitimate reason for denying the American-based unification of that family. (González was a pawn that both governments used to placate a miserable status quo.) The relevant point here is that the provision for migrating the González family to America was (and still is!) a viable and logical _option_ (not a requirement).
Again, government is a proxy for (and an extension of) an individual's survival mechanism. That is (noting the division of labor principle), government is hired by citizens to do a far more efficient job of protecting the citizenry than those citizens could otherwise do for themselves in a direct way. Some consequences to take note of: 1) This indicates why ideas such as "Let's make a Mulligan's Valley/Galt's Gulch today!" or the Libertarian "free-state" project are absurd. For one thing, there necessarily has to be a central authority (noting AR's reprisal against state fragments viz. "50 tyrannies vs. 1"). Also, there must be minimal proper philosophical and psychological standings in place i,.e. the specific populations of those breakaway groups would have had to already express the sanity let alone the comprehensive understanding to know the conditions for preserving and protecting freedom given that context. In point of fact, they would have to be _more_ sophisticated than the Founders in certain respects, and that is _highly_ unlikely to happen in the time before America is reconstituted as a rights-adhering nation. (Among other fallacies, that presumption of theirs involves question-begging... In point of fact, those type of idealists are also pretentiously dropping the context that neither are a) the national conditions synonymous with those in _Atlas Shrugged_ in the relevant respect nor b) do those idealists have altogether substantially greater facility than other Americans when it comes to the required "nation-building" skill sets.) 2) Likewise, another false alternative in the form of anarchism is absurd given that (as I already just mentioned) there's more than a passing role for government. The distinction between the actual government functions and the myriad of social benefits that Marxists approve of is well-defined, so not all of government need be considered pointlessly lost and useless. 3) The 2nd Constitutional amendment exists as a backstop acknowledging that a citizen's right to physical self-protection is to NEVER be abrogated under any circumstances even if that means having the citizenry taking on a failed government that was supposed to be responsible to those citizens. Suffice it to say that negotiating the time to fight a government in such a way is off-topic here and requires a fair amount of elaboration itself. (All rights are derived from an individual's existential nature of being a "rational animal".)
As Ayn Rand spent multiple decades expounding on, rights are the means to preventing others from initiating force against oneself (while presuming that one will respect the norm in kind). _The Virtue of Selfishness_ is the definitive starting point in understanding the (Objectivist) ethics, so consider that to be the underlying normative background for this issue.
The core government functions are represented by the police, the military, and the legal administrators (The Supreme Court, The Congress, and the Presidency). Naturally, the obverse holds accordingly: The other "alphabet" organizations are counter-productive, tax wasting, and wholly immoral. Naturally, core government functions can't be implemented without supporting staff. With this in mind, there _are_ a few government agencies that are worth considering as legitimate supportive bodies.
I have personally wrestled with what value the USCIS (INS) might actually have in the aforementioned respect. Predicated on the premise that maintaining the nation's existential integrity is paramount (relying on the Objectivist ethics), I believe that the USCIS should be considered as a legitimate aspect of government ...under the guise of the military. Note that immigration is physically unidirectional. It is not primarily a matter of citizen travel (no more than the 2nd amendment is about game hunting)! Because government is singly concerned with rights protection, the first obvious immigration-related question is: What threats does immigration pose to the American citizenry? There are precisely 3 types of threats that are involved: 1) Serial aka "career" criminals who simply seek to take undue advantage of rights-respecting citizens in the usual ways of domestic violence that police must contend with 2) State-affiliated terrorists who for a variety of specific motives want to threaten the U.S. government itself which the military must contend with and lastly 3) Pathogen-carriers who have the potential to cause epidemics which most anyone in government may have to deal with due to the metaphysics involved. The reason for cordoning and then expelling the 3 types is essentially the same. They are all an explicit and outright threat to the greater populace. That is to say, those threats can violate the rights of masses of citizens simultaneously. Leaving aside ancillary concerns e.g. trying to get military intelligence from a capture, those who represent any/some of the 3 threats should without exception be immediately captured and controlled and in all likelihood also transported beyond U.S. civilian borders _at minimum_.
See here for the relevant Immigration Services mission statement for current status:
http://www.uscis.gov/aboutus
Likewise, the Border Patrol should also completely be subsumed by the greater military services. Obviously, the rationale for this is synonymous with that of subsuming the USCIS. From a practical point-of-view Aristotle's identity axiom is the most fundamental principle. Considering that philosophy is the foundation for all science, normative principles are themselves philosophical concretizations (while being abstractions in respect to everyday behavior i.e. teleological specifics). Naturally, Ayn Rand had quite a bit to say on this as well as on the relevant antecedent ethical theory. A value "is that which one acts to gain and/or keep." In concrete terms, if America fails to differentiate itself from the other nation-states which are currently not based on the same basic normative concept, then America itself loses value and vanishes (which would in turn, extinguish all other derivative values). In other words, America's borders mean the life or death of the nation just as a person's epidermis (including all cilia, etc.) exists as the differentiating factor between potential life or death as far as the physical elements are concerned.
See here for the relevant Border Patrol mission statement for current status:
http://www.cbp.gov/about
The above represents the _entire_ general border control policy as far as philosophy goes. Because normative principles are still abstractions as far as specific events are concerned, it is naturally important to further concretize them for immediate application. Understand that that point of application is where general philosophy already ends and where specialization begins.
To wit:
Some have concerns regarding illegal aliens inside the U.S. It would be good to remember the most important inscription excerpt on the Statue of Liberty:
Give me your tired, your poor,
Your huddled masses, yearning to breath free,
The wretched refuse of your teeming shore,
Send these, the homeless, tempest tost to me,
I lift my lamp beside the golden door.
Your huddled masses, yearning to breath free,
The wretched refuse of your teeming shore,
Send these, the homeless, tempest tost to me,
I lift my lamp beside the golden door.
http://www.scrapbook.com/poems/doc/3061.html
Assert the principle; it isn't an accident or a matter of caprice whereupon Ayn Rand fundamentally associated America's identity with the virtue of independence.
Those who have crossed U.S. borders illegally and subsequently have lived in America while working to better their respective lives without taking undue resources have presumably only broken the one law. We aren't mindless machines. If and when illegal immigrants are found, then ask them a simple question: "Do you wish to continue to live here after complying with the law?" If they say "no", then send them from whence they came. If they say "yes", then put them through the naturalization process. It is the ultimatum that they asked for and deserve, and that is that. (_All_ other related concerns e.g. potential for broken families and/or job cancellations are logistical matters or ideological derivatives.)
Other threats (such as the D.C. sniper from several years back as well as current Ebola fears) can and should be likewise resolved in general as follows: Identify the physiological (including psychological) and philosophical (including political) status of the threat agent, and then process such a threat given the pro-American/Capitalist paradigm. To put it differently, there are no gray areas, fine lines, or mysteries ultimately. Once the nature of the threat is understood, that threat can be categorized and then processed. It is incumbent on the American people to understand that a so-called "threat matrix" has no need for "complexity worship". On the total contrary, thinking in essentials leads the way to reconciling any and all extant threats to America without unnecessary haste or confusion.