"Promotion of this offer to underage users forbidden" (fair enough!)

[AffiliateNate]

I'm wondering how you guys deal with this. On the traffic sources I use there is no option to filter by age. Do you just put a prelander asking the user's age and then not promote the offer to those who are not 18+? Or is there more to it? I ask because some networks threaten an immediate account ban / voided payments if the rule