"A shield an enemy uses to prevent capture but you can break it by waiting for the meter to charge, and then press A. The power surge should be enough to disable their shields"'"—E. Gadd, Luigi's Mansion 2
A Paranormal Shield is an object that grants ghosts invincibility in Luigi's Mansion: Dark Moon, until it gets shattered by an electric pulse from Luigi's Poltergust 5000. The Paranormal Shield can be a different color in different areas, which indicates the level of the power surge that is at least required to shatter it.
In the Dark Moon Quest, Paranormal Shields are introduced in mission C-4 "Play Catch" where a single Greenie in the Warehouse uses it. In ScareScraper, only the Beetle Whisperer and its variations of them use the Paranormal Shield in normal mode. During harder modes, other ghosts such as Greenies use it.