▁laws . ▁Since ▁state ▁ins pe ctions ▁were ▁carried ▁out ▁on ▁land , ▁for ▁both ▁imports ▁and ▁exports , ▁a ▁" tax ▁or ▁duty ▁of ▁ins pection " ▁was ▁" fre qu ently , ▁if ▁not ▁always , ▁paid ▁for ▁service ▁performed ▁on ▁land " ▁once ▁the ▁imported ▁item ▁was ▁within ▁the ▁country . ▁Marshall ▁thus ▁concluded ▁that ▁" th [ e ] ▁exception ▁in ▁favor ▁of ▁duties ▁for ▁the ▁support ▁of ▁ins pection ▁laws ▁goes ▁far ▁in ▁prov ing ▁that ▁the ▁fram ers ▁of ▁the ▁Constitution ▁class ed ▁tax es ▁of ▁a ▁similar ▁character ▁with ▁those ▁im posed ▁for ▁the ▁purposes ▁of ▁ins pection , ▁with ▁duties ▁on ▁imports ▁and ▁exports , ▁and ▁supposed ▁them ▁to ▁be ▁prohib ited ." ▁However , ▁he ▁found ▁that ▁this ▁narrow ▁view ▁of ▁the ▁subject ▁was ▁not ▁enough ▁to ▁strike ▁down ▁the ▁Maryland ▁tax ▁on ▁im por ters ▁and ▁proceeded ▁to ▁examine ▁the ▁motiv ation ▁of ▁the ▁Found ers ▁in ▁including ▁the ▁Import - Export ▁tax ▁and ▁its ▁role ▁in ▁the ▁federal ▁framework ▁of ▁the ▁Constitution . ▁ ▁Imp ost s ▁and ▁duties ▁on ▁imports ▁and ▁exports ▁was ▁a ▁subject ▁given ▁sole ly ▁to ▁Congress , ▁" plain ly ▁because , ▁in ▁the ▁general ▁opinion , ▁the ▁interest ▁of ▁all ▁would ▁be ▁best ▁promoted ▁by ▁placing ▁that ▁whole ▁subject ▁under ▁the ▁control ▁of ▁Congress ." ▁Reg ard less ▁of ▁whether ▁that ▁power ▁was ▁to ▁prevent ▁state ▁tax ation ▁from ▁dis rupt ing ▁harm ony ▁between ▁the ▁states , ▁prevent ▁states ▁from ▁h ind ering ▁uniform ▁trade