We don't have any way of blocking buyers by IP, as that's quite futile and more likely to block legitimate buyers than fraudsters, who already quite commonly change their IP address with every attempt, simply by resetting their router or visiting different public wifi hotspots; if they're sharp enough to use different emails, they're almost certainly already using different IPs as well. Blocking an IP they've already used would simply block everyone else who happens to use that hotspot in the future, or who happens to get randomly assigned that IP by their ISP the next time they connect.
