Assembly not found in SQL Catalog

I don't believe this. Searching for my second day now.
All I want to so is create a CLR stored procedure which can access VSS on my own machine. I'm running into this when I try to deploy...

Assembly 'microsoft.visualstudio.sourcesafe.interop, version=5.2.0.0, culture=neutral, publickeytoken=b03f5f7f11d50a3a.' was not found in the SQL catalog.

Is it possible that only a limited pre-listed assemblies can be used for reference in a CLR procedure?

Here's the solution...