At best you can assert suspicion, but I've not seen this case being made.
As to legal standards, what you assert past positive test(s) (actually one - see
http://www.usada.org/wp-content/uploads/AAA-CAS-Decision-Justin-Gatlin-January-2008.pdfpage two where USADA basically says first wouldn't have been a positive but for failure to properly/timely file paperwork ), lack of genuine contrition (very weak in terms of being dispositive, even if it's assumed for the sake of argument) and current performance (can raise suspicion but if he's passing his tests good luck with this in a court of law) - is extremely weak.
You can be suspicious and want him to be guilty, but I've yet to see anything be asserted with solid evidence (your post supports suspicion NOTHING more) that approaches probability let alone proof beyond a reasonable doubt. But of course this is LRC, everything is subject to suspicion and all accused are guilty. Critical thinking and due process are tough and don't provide the immediate satisfaction of smug self-righteousness and compensation, via vicariously "participating" in T&F, for feelings of inferiority.