Consitution states that slavery is left up to states, how was the Dred Scott case be constitutional?

Basically, the question above. If I remember correctly, the constitution states pretty clearly that slavery was a decision for states to make. If so,

Basically, the question above. If I remember correctly, the constitution states pretty clearly that slavery was a decision for states to make. If so, how could the dred scott constitution (a decision that stated even free black men and women could be recaptured into slavery) have been allowed to stand?

or:Basically, the question above. If I remember correctly, the constitution states pretty clearly that slavery was a decision for states to make. If so, how could the dred scott constitution (a decision that stated even free black men and women could be recaptured into slavery) have been allowed to stand?

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