I think the effect would probably be more limited than that. The same con artists (I work on the basis that believing your own lies makes you incompetent, not a truth teller) will still offer the same chargeable consultation services and as before, and then will flog you the same jar of wishes for your ailments.
Unless homeopaths, or whatever they are called, are criminalized and driven underground that is. That would entertain me, which I hope is deemed sufficient reason to do so. Actually that could be the basis for an amusing dystopian fiction.
Otherwise they would be barred from displaying certain certificates of medical worth that by definition their clients rarely look for; perhaps they can no longer receive direct referrals from the few GPs who consider them something other than placebo vendors; and presumably they will no longer be claimable on insurance or funded by the Belgian NHS (to whatever extent either ever applied).