From the Super Mario Wiki
Enemy Blocks are a special kind of blocks found in the Wario Land series. They are commonly featured throughout many levels and serve as obstacles, blocking Wario from accessing certain areas. These solid blocks cannot be destroyed by normal means. To break through them, the players have to pick up a stunned enemy or a portable object and throw them at the obstacles. The impact will then break the blocks, clearing the path for Wario to progress further.
Wario Land series
Enemy Blocks appear in Wario Land II for the first time, where they are red in color and have an image of a Pirate Goom imprinted on them. Sometimes they can also be found hidden in walls or pillars. Wario Land II's predecessor Wario Land 3 also features Enemy Blocks, though they are now bright pink and sport a different symbol. They can also not be broken before Wario obtains the Red Glove, since he cannot pick up any enemy until then.