Preventing Authors from posting images linked from other sites

Hi all,

Although it’s been a week searching for the solution but no joy ??

The problem is with some of our authors posting posts and in those posts they sometimes use images hotlinked from other sites/blogs. This is indeed something I want to prevent from happening.

It will be of big help is someone knows a plugin or a “hack” to prevent authors from posting images linked from other sites.

Thanks in advance,

b.