A proxy works somewhat like a NAT. People usually use 192.168.x.x or 10.10.x.x as their ip addresses on their LAN, but the outside world will not see these ip addresses. The ip address they see is their IP issued by their ISP. Well, the proxy does the same thing, but using public ip addresses. Just like how you connect through your router and it masks your local private ip address. Going through a proxy shields your ISP's ip address from the world. The proxy replaces the ISP's IP address with it's own. So when the ACL filters ips and has yours on restriction, it will only see the proxys. Just try it and it will work.