Restrict Download as .zip

[Filigree]

In regards to the .zip download feature, is there any way to restrict who can use it?  I would prefer that only members be able to download files from my gallery.  However, guests are also able to add files to "My Favorites" (because it works on the principles of session cookies I assume) and download them as .zip files.  How can this be prevented without turning off the feature entirely?

[Tarique Sani]

Sorry currently the feature is all OR none ...