The drawbacks of legalization do not imply that our current version of prohibition is the optimal drug strategy; it may well be possible to implement prohibition in less harmful ways.
The drawbacks of legalization do not not imply that our current version of prohibition is optimal.
the wording means it does imply so the statement is incorrect but the AI did not catch the trick in the wording so marked it correct.
( z1 imply :polarity - :ARG0 ( z2 drawback :domain ( z3 legalize ) ) :ARG1 ( z4 optimal :domain ( z5 version :time ( z6 current ) :mod ( z7 prohibit ) :poss ( z8 we ) ) ) )