drug trafficking, illegal immigration don't serve as counterpoints; you're putting the cart before the horse
The drugs trade is the flow of narcotics from source to sink. Stopping them at a national border is one approach; stopping them elsewhere in transit (as it leaves the source, on the open sea, at the destination by local police, etc) is another. And then you have one more: tackling the existence of a source and a sink. In other words, you look at supply (i.e. creation/generation of stock) and demand. I believe that this is perhaps the best approach, and it is definitely one to which borders are irrelevant. So I don't really accept that as a counterpoint to what I was saying. In some ways, the fact you thought it was illustrates my point: our focus on borders is simplistic and maybe distracting us from finding more effective approaches that might be inspired by a thorough analysis of the system dynamics.
People trafficking is to some extent the same thing: source, sink, and a flow over many miles from one to the other (maybe across a border, maybe not).
As for illegal immigration, you have a flow that exists because of inequality (i.e. it's a flow down a gradient) - a difference in living standards, job opportunities, safety, etc. This inequality makes the recipient country a sink and the donor country a source. But of course, once again we shouldn't be talking about countries. Some regions are more attractive than others, and people have always moved between them, generally to the gain of one region and the detriment of another. Population flows can be cross-border, or not, despite the similarity in causes. Once again; should borders really be the focal point at which destabilising migrations are addressed by modern, globalised societies?