In Voyager episode 24 of season 4 'Demon'.
Background: The ship is running low on deuterium and they locate a Y class 'Demon' planet that has large deposits of the needed molecule. Harry and Tom visit the planet to locate and take samples. The planet is covered in a metalic-like liquid that creates copies of the 2 crewman when they come into contact with it. At the end of the episode the Captain allows the crew to give DNA samples in order to create clones of any willing crew members and leave them there to colonize the planet with the new life-forms.
My question is whether or not you believe Janeway made a severe ethical breach by allowing this to happen. For one thing the clones (due to only being able to breathe the native atmosphere) must remain behind on the planet.
Throughout the episode, both Harry's and Tom's clones demonstrate their fond connection with the planet and desire to remain there. This, I believe, was done specifically to quell any concerns the audience might have for this exact question. But Janeway could not have known, for sure, that this would be uniform trait among ALL clones. What if Tom and Harry ended up being the exception to the rule?
Admittedly, Janeway let individual crew members decide if they were willing to clone themselves but the instant the clone is made, it is its own, sentient, life-form. What if the clone decided it didn't want to stay on the planet? Essentially, it would either be stranded on a miserable planted that it had no say in being on, or die. The clones' fates were decided for them before they even existed. For all we know, the planet might not even be able to sustain the new colonist long-term.
Additionally, there was no time to find out if there might be potential complications with the new clones that didn't yet have time to reveal themselves. I could think for hours of potential issues that were not even considered (at least on screen) or issues that could not be planned for until after the clones were made (by which time, there is no going back.) Basically, in the span of a 30 second conversation with clone Harry, Janeway made a decision that, very possibly, could result in her being responsible for slowly mass-murdering and imprisoning (via stranding) almost 150 people.
Note: This question is not if Janeway violated Federation law or the Prime Directive, but human ethical notions.