StyleCop rule for checking project references

Sometimes, when updating a dll version, references to this DLL from other projects suddenly link to the GAC and not our custom assemblies folder. This is a problem because the project may reference an old dll and will not deploy in a TEST environment.

So I want to create a StyleCop rule. The rule is to check if the project references are referenced by the GAC. If they do, a warning or error must occur. I found documentation on how to create custom StyleCop rules, but I need help getting started.

So the question is, how do I access the project links via StyleCop, so I can check if they point to the GAC or not? Or do you know a tool that checks project references?

Thank you in advance