This is an interesting concept... can an individual, or organization, declare "war" against a corporation and actively try to do them harm and/or destroy them as an organization?
Of course they can, big corporations do this regularly to the smaller corporations. But this "war" wouldn't fit any universally accepted definition of war so I don't know why would you want to declare anything, just do what you want to do. It is really interesting that a lot of people think that the best solution to any problem is to declare war to said problem, either real war or just "war".
Ocean: A body of water occupying about two-thirds of a world made for man -- who has no gills. -- Ambrose Bierce