Depends if we assume they're smuggling or dropping explosives/something dirty.

Suppose they are smuggling narcotics.

Okay, since economics has extensively studied the effect of narcotics on the economy (which is positive, or to put it another way: people will work, even fight, for drugs), we can clearly establish that the cost of missing a shipment is negative. For the economy, it is actually better to miss the shipment than to catch it.

So allowing Mexican cartels to smuggle and sell, for example, heroin has a positive economic effect on society? I have to admit that's a fresh perspective.

But you neglect to take into account the perspective I mentioned. Heroin certainly makes money go round and therefore helps GDP.

We just, as a society, have decided that the social cost is not worth it.