No, you can not enforce your will on another web site that you do not control. 🙂
You can only access whatever is accessible via HTTP. You can do what web spider bots do and look for links in the pages you know about, check to see if there are any sitemap.* files that give you pages to look for, etc.; but that is in no way guaranteed to find everything. There is no way I know of via HTTP to just say, "Show me all the files in directory such-and-such."