At issue: firms that provide drugs for lethal injections squander "goodwill", an accounting term-of-art meant to measure the dollar value of brand loyalty or public trust the firm enjoys. It's bad for business to be seen as the merchant of death, I suppose. The EU has even gone so far as to threaten an embargo against the US if the several states continue to use Eurozone-manufactured drugs to execute prisoners.
The dropsman, the burly axeman, that grim bareback stretcher of necks, Le danseur du Madame Guillotine, the Final Servant of High Justice, the Scharfricher... call him what you will, but almost universally, this man is hooded to protect his identity lest he become a pariah. Ottoman Imperial executioners were drawn only from Romany stock, untouchable wandering peasants. I strain to imagine a historically lower status profession over the long arc of written history. Dung heap shovelers never needed hide their face for fear of community reprisal. Cold-blooded execution, even if directed by the impartial arm of the Law, is simply reprehensible, atavistically so. Execution is not euvoluntary (duh).
Curious: why wouldn't the exact same moral intuition apply to the many, many, many firms that deal either directly or indirectly with state agencies responsible for casualties incurred in the many armed conflicts around the world. Drugs that end the lives of heinous criminals are one thing, bombs that end the lives of innocent children are something else entirely. How many Eurozone firms conduct commerce with General Atomics Aeronautics (the company that makes Predator drones)? How about General Electric, with their immense DoD contracts, or Westinghouse, or General Dynamics? Are EU political elites threatening to embargo these firms? Why not? What's the difference?
In Arnold Kling's 3-axis model, the conservative axis has that state executions are barbaric, and rehabilitation is civilized. The progressive axis would suggest that criminals are (perhaps) the result of oppressive power structures, and there is no justice in an execution—though I confess I'm not sure how the use of drone warfare would square with the moral intuition on this issue. And for libertarians? I don't think I'm familiar with a definitive libertarian stance on capital punishment. I don't think there's much marginal deterrence compared to lifetime imprisonment, and there are convincing deontological arguments both for and against.
At any rate, it's worth it, I think, to revisit from time to time the question of whether the state has a compelling interest in executing its citizens for heinous crimes. I also think it's worth considering if there can be justice in exchange when the telos of the trade is to end human life. I also think that to be consistent with principles of universality and fairness that considerate euvoluntary exchangeurs should give some thought to examining a wide range of trades, not merely those that offend moral sensitivities inherited from distant times. Perhaps it is immoral to hawk pentobarbitol to the headsman, but perhaps also it's just as immoral (if not more so) to sell guidance systems that'll sit in a GA MQ-1 Predator.