Proper use of gacutil.exe

I would like to know why everytime I run gacutil.exe it always
includes a CodeBase of "file://...", following the Microsoft
instructions for usage of gacutil.exe I'm trying:

gacutil.exe /if MyLib.dll

This command always results in an entry in the GAC that includes a
CodeBase reference (which I believe is causing some problems), none of
the other Assemblies in the GAC have a CodeBase attribute so there
must be a way to run gacutil without registering this.