AFAIK, pre-loads aren't open yet, and there are no wordings from either Activision, Steam or Treyarch (for what they're concerned). This dates to about 7 hours ago, haven't checked since then.
They'll likely open about 2~3 days before release tho.
However, if I were you, I wouldn't order from G2A, or kinguin, or whatever gray market e-retailer you stumble across unless you're 100% the key's source is safe. Buying a game for potentially 1/3 the price for the risk of getting it banned? Just my two cents, but I'd rather pay in full.