Once such an archive existed, medical journals could adopt a policy of checking all citations in a proposed article against the archive, rejecting submissions that tried to cite refuted research as valid.

The problem with this is that power corrupts. Medical science is already suffering from group think problems this would likely make it worse.

Nancy mentioned Polifact here, I'm pretty sure I've seen controversy over some of their pronouncements. In any case I'm sure they'd be much worse if they had actual gate-keeping power.