I don't know what exact scenario you are talking about here.

Even a huge construct (1000 tons?) at escape velocity has less energy than the smallest of nuclear weapons (20kt), and a tiny fraction of the explosives used in mining right now (at least megaton TNT equivalent/year).

> By the way, are you sure the control systems of the mine owners are resilient to coercion of their executives by "legitimate" terrestrial governments? I'm not. None of your reasons are effective.

Are you just playing devils advocate here? There is few things that I'm less concerned about than mining explosives being confiscated and repurposed for some shady-government terror campaign.

> If North Korea or Iran could hold the world hostage with a threat of a mass-extinction-level event, they absolutely would. Similar for many terrorists of various stripes. Are you sure the control systems of whatever company ends up trying to bring back mass from space will be sufficiently resilient to hacking? I'm not. So, I worry.

North Korea has weapons of mass destruction already, and delivery vehicles for them. So what? Those destructive capabilities are already much greater than anything they could ever hope to gain from ursurping some space-mining operation within the next centuries.

Russia has even greater capabilities and plenty of imperialist desires to fulfill, but those nuclear threats did not seem to help them gain anything of consequence over the last decade, and not for lack of trying.

The thing is that any organization wealthy/powerful enough to realistically gain access to militarily relevant systems will typically also have enough to lose to disincentivize haphazard use. Rare exceptions like 9/11 demonstrate how much circumstance is required to get around this.