"I notice Kerry said no BACK DOOR draft, but DIDN'T say NO DRAFT"

Context - both verbal and situational - is important when listening or reading. A specific mention of backdoor draft is warranted because one currently exists. No mention of a regular draft does not imply an intent to create one. Instead, no mention may be necessary because one does not currently exist. For example, is it telling that Kerry did not promise that he would NOT require military personnel to fill their boots with lemon cream? Does this imply that he will require such? Oh my gosh.