Your dad is right most states allow blackpower/muzzleloaders during regular rifle/gun season. Why because it's a legal hunting tool. Same as using a handgun. Now most states have definitions of a legal hunting tool...muzzle loader of greater then .40cal, or say handgun round with muzzle energy of or greater then @#*&.. The States that gun season means shotgun season, may or may not allow muzzle-loaders. I would use my muzzleloader over a shotgun with slugs, because my muzzleloader shoots better then any shotgun with slugs I own. Another reason someone would use a muzzleloader over a rifle or shotgun is if they were a convicted felon. Convicted felon's are prohibited from using firearms, however most are allowed to use and own a Blackpowder/muzzleloaders.