It's time for a little honesty about Ron Paul, particularly his position on immigration. While Ron Paul is all the rage in libertarian circles right now (for some very good reasons), on certain issues he is more of a right-wing populist or paleo-conservative. Whenever he "deviates" it's in the socially conservative direction, on issues such as immigration. He certainly is the most libertarian person to be in congress for a long time, but one should also be aware that he has affinity with the Christian right and other such groups.
Immigration restrictionist policies (immigration quotas, illegalizing immigrant jobs, publicly-funded walls, federal control of state's borders, etc.) are government interventions, economically and otherwise, and therefore are outside of the realm of libertarianism. Interventionism X (welfare) does not justify intervention Y (police statism and protectionism). Ron Paul is appealing to the sentiment of right-wing populists like Pat Buchannan on this issue. Aside from those who follow Hans Herman Hoppe's immigration position, and many Ron Paulians, no libertarian in their right mind supports immigration restrictionism.
Like all anti-immigrationists, Ron Paul uses the welfare state (the real problem) as an excuse to persue other government interventions such as publicly funded walls and mass-deportation. His vote for things such as publicly funded walls should be pointed out as unlibertarian by any libertarian with two cents. The fact that people suck off the welfare state is not an excuse to forcibly remove them from their own property or illegalize their jobs. Domestic citezens are "guilty" of just the same, on a much larger scale than immigrants ever will be.
Furthermore, the arguement is nonsensical in that for the most part illegal immigrants do not qualify for those government services; it is the legal citezens who do, and it is the legal citezens who are at least partially responsible for supporting it. There is no moral difference between a legal citezen and an "illegal" sucking off of the welfare state. All of the welfare-related complaints about illegal immigrants apply equally to domestic citezens. Under this logic, therefore, domestic citezens should be deported and have their jobs illegalized as well.
Ron has fallen into the trap of interventionism on this issue. Mises's critique of interventionism applies here. That is, interventions are proposed as a solution to past interventions, rather than a repeal of the previous intervention. The initial intervention is the welfare state. But, while he has tried his best to oppose the welfare state, Ron Paul falls back on supporting new interventions as a "solution": government-funded walls, immigration quotas and deportation. If one seriously thinks that this is going to solve "the problem", then one is fooling oneself. In practise, this will result in a further march towards a police state, more growth in federal funding, and meanwhile immigrants will still get through "illegally", just like before.
That is only on the consequentialist side of the arguement. The other side of the arguement, and the more important one, is that it's a violation of property rights to (1) force someone off of their voluntarily aquired property or force a landlord to evict a tenant (2) to illegalize someone's voluntary employment agreement; this too violates the property rights of both the immigrant and the citezen associating with them (3) to siphon funds from the tax-payer to build walls (4) to initiate force on someone for crossing unowned land and (5) in general, to force people to dissassociate with eachother on their own property. What do all of these things have in common? They are inherent in anti-immigration policies.
Ron Paul's position on immigration is better then Pat Buchannan's, but it is not too far off from it. While he does not openly champion protectionism, he still supports the police enforcement side of the equation in the name of "constitutionalism", and makes a somewhat Buchannite arguement with respect to how the welfare state relates to immigration.