Customs officers the world over are corrupt. Not all of them, but how many do you need to be corrupt in any given jurisdiction for handguns to become a hot smuggled item?
Every drug/prostitution/standover gang in Australia has zero problem getting hands on Glocks and submachine guns -- despite very stringent gun ownership laws.
My views on gun ownership are well known. Let's not get into a pointless argument about this.
Ignoring what I think about the right to bear arms, what cannot be denied is that a criminal will always be able to get hold of a gun. You or I can't do this because if we get caught with an illegal firearm, we go to prison, get a conviction record, and destroy our good little sheep citizen future employment prospects cum financial futures and eventually die impoverished on the old age pension eating dog food.
Strangely enough, criminals don't care about criminal convictions and a year or two in the slammer -- which they had coming every now and then anyway.