the transporter made them - meaning the transporter works by copying people.
But it's portrayed as a freak incident, not a regular occurrence. If the transporter made duplicates, there would be little problem in making Moriarty real, reviving old crewmates, or creating massive armies of people instantly.
It's supposed to be conversion into energy and conversion back into the same structured matter. That's not really copying, it's just shifting things around.
Ryan8bit, a human body is incredibly complex. ANYTHING that can copy a human body perfectly WAS DESIGNED to copy it; otherwise, the copy - if a freak accident created one - would be a failed genetic experiment.
Yes, I know the conventional explanation for the transporter is - your atoms are transformed into energy, the energy travels to a point in space where it;s transformed back into matter. But the presence of TWO Rikers directly contradicts this explanation - no system like this can create an identical copy of something it transports.
Moriarty was a hologram - fotons and force-fields - and a copy of a hologram is still a hologram.
And yes - with this transporter you CAN create duplicates of people - as the Rikers DEFINITIVELY PROVE. Why isn't it used in this capacity?
Real-world answer - the scenarists didn't think the technology through.
Trekverse answer - an absolute moral interdiction? That all species share

?
I'm no expert, but I think the bible according to my father considers killing and murdering to be two seperate things as in original translation 'Thou shalt not murder instead of Thou shalt not kill.' He also said killing soldiers during war was legal as was self defense. Just sayin'. I personally wouldn't go to war or kill anything other than the occasional spider but then again I'd be living under Hitlers rule, wouldn't I ?
O, but there's a difference between killing a thief who intends to kill and rob you and kill an enemy soldier who just wants to come back to his family and forget about the war and its horrors - much like you.
Are both cases self-defense? Yes - but in one, your choice is a lot 'darker'. The grotesqueries of war, as it were.
But what if you receive the order to wipe out a village full of civilians, an order deemed 'legal' by your government?