What is the goal of the java.nio.file.CopyOption interface?

I'm confused about the design of JDK7 nio package (which I use often). Take for example Files.copy, which takes instances of CopyOption's which is an empty interface, e.g. implemented by StandardCopyOption:

public enum StandardCopyOption implements CopyOption {
    REPLACE_EXISTING
    COPY_ATTRIBUTES,
    ATOMIC_MOVE;
}

public interface CopyOption {
}

What is the idea behind such a design? I mean, even though the CopyOption interfaces is passed to Files.copy, Files.copy has still a compile-time dependency on StandardCopyOption (see source-code of Files.copy).