This worries me.
In computer security, you have a firewall on the edge of your network, but that's been long proved ineffective against most indirect attacks (ie. viruses, internal hackers, software failures etc). The current thinking in this area is to firewall each computer on your network, and to improve the quality of the software on those machine such that software failure and viruses have less chance to take hold.
It seems immigration policy is back in the 90s. Putting a "hard outer shell" around a country isn't going to achieve what is required. It only takes some weakness in that shell to be exploited and you have a steady stream of possibly dangerous people coming in. Like firewalls, only the more talented intruders will gain access, so whilst the numbers go down, the concentration of danger is higher.
Like network security, protecting each entity seems a sensible idea. Replace "software quality" with pride, social conscience, community understanding and awareness. Now you have a self-healing nation (self-healing currently being seen as the holy-grail of network security). Any potential threat is identified by vigilant citizens, and most probably thwarted without direct action, possibly without even meaning to do so. Further, the rise of disgruntled people is stunted because people feel a sense of responsibility and belonging.
The world no longer works by lining up one's "big guns" and hoping to "out gun" their opposition. It's far more subtle and complex. Now the greatest military force cannot be used against insurgent terrorism. You can't carpet bomb your own people, so your military stand idle. The "war on terror" (as if that's the right way to describe it) now relies on information, on behavioural analysis and on basic investigative skills.
Again, the world of IT has a possible paradigm here. Open Source and distributed development have proven that they can build software faster and in many cases, better than old closed methods. Interestingly, software security benefits most from this paradigm, as more eyes look upon the problem, more issues are found and fixed. The same could be true of anti-terrorist intelligence. The security services could never hire enough people to rival an "open source" scheme.
Of course, creating an "open source" anti-terror scheme requires a far longer term, and far greater commitment than bolstering one's security services and bombing a few countries. It requires that people care about their neighbourhoods, their towns, cities and country in a way not seen for generations. If you genuninely cared, and were not scared to confront possible miscreants, then the likelihood of them having any kind of success is far reduced.
To achieve this takes real guts, takes the very strongest of leadership and the most transparent, accountable and democratic government. Does such a thing exist? If not, could it?