I have read Interfacing with GPL applications from MIT licensed code - is a dual-license unavoidable? (now deleted) on Stack Overflow, but it doesn't appear to fully answer my question.
I maintain a library which is licensed under the MIT License. In my MIT licensed library, I dynamically link (Python ctypes to be specific) against another library which is licensed under the GNU Lesser General Public License 2.1 (LibRaw). This would be fine by itself, however, LibRaw is sometimes statically linked against a sort of "plugin" called the LibRaw Demosaic Pack which is licensed under GNU General Public License 2+ or GNU General Public License 3 depending on the version. I have no way of checking if LibRaw has been linked against these libraries. (LibRaw is just installed on the end users computer and when they download our library and use it it links against it, I am not redistributing or building LibRaw.)
Does linking against the LGPL library from my MIT library when the LGPL library has been linked against GPL code mean that I'm illegally using GPL code in my MIT Library?
If it is so, is there some way around this short of sub-licensing parts of my code under the GPL, or dual-licensing (which is just confusing for the end user)? Or can I still link against the LGPL library under the terms of the LGPL even though it then links against GPLed code?