SSPS military applications - crit please

We all know that SSPS can in theory solve the world's energy problems. But
could it also solve others? I'm toying with a novel in which a cylinder
colony has to deal with an uncouth planetary nation which lacks space
capacity.

Their solution is to place an SSPS in GSO, mount cameras and
JHPSSL-descended gigawatt lasers on it with 200m wide adaptive mirrors, and
programme it to destroy anything human or man made crossing the nation's
borders. Without international trade (the colony believes) the nation would
fall into the dark ages and become more moderate, either because survival
takes a higher priority than extremism, all the extremists die out, or the
majority population rebels against idiocy.

Assuming that no third party interferes, and a reasonable amount of second
world industrialisation, what are the problems of this proposal, and what
might the planetary nation do to either destroy the satellite or make border
crossing survivable again? Personally I think they're probably SOOL, but I
might be wrong. How effective would this be?

John