This can only occur on original Militarized Hegemony Auxiliary ships, either purchased on the market or salvaged. It will not be removed by restoring the ship. Ships with this hullmod are usually denoted with an "(A)" suffix to their class name.
The Militarized Hegemony Auxiliary hullmod is most often found on civilian or logistical ships, or those ships that are not primarily designed for pure combat. It is generally mutually exclusive with the Civilian-grade Hull hullmod, removing the latter on those ships that would otherwise have it (such as the Buffalo and Kite), which makes them highly desirable as they do not suffer the usual civilian ship sensor penalties.
Only up to date for version 0.8a-RC19. It is likely still broadly correct but not verified for the most up to date data yet. Please double check the Version History