Which design pattern for my proxy Rule

I have a proxy HttpHandler that gets a url from user as a querystring parameter like following.

public class MagicProxy : IHttpHandler
{
    public void ProcessRequest(HttpContext context)
    {
       string requestUrl = HttpUtility.UrlDecode(context.Request.QueryString["url"]);
    }

    public bool IsReusable
    {
        get
        {
            return false;
        }
    }
}

url parameter is like this:

http://server1.com/service?method=get&request=GetInfo
http://server1.com/service?method=get&request=GetFeatures
http://server1.com/service?method=get&request=GetImage&Format=PNG

I am parsing url querystring. Because some users can use method=get and can not use method=post. Some users can use request=GetInfo and some users can not use reguest=GetImage.

These are my rules by users. I want to use desgin pattern to implement these rules. But I could not decide to use. Specification, Strategy, or else. I am new at desing patterns.

public interface IRule{}
public class UserCanUseGetMethod:IRule{}

How can I combine rules and user?