§  306.  A  curious  and  important  question  has  arisen  from
the  exercise  by  Congress  of  its  power  to  tax,  which  may  be
referred  to  in  this  connection.  When  the  United  States  has
established  a  system  of  excise  duties,  and  among  other  things
has  required  that  persons  carrying  on  certain  kinds  of  business
shall  pay  a  license  fee,  and  take  out  a  license,  can  a  state  inter-
fere with  persons  who  have  complied  with  these  requirements,
or  prevent  them  from  prosecuting  the  particular  business  for
which  they  have  received  a  national  license  ?  No  case  has
arisen  which  answers  the  question  thus  put ;  for  the  internal
revenue  law  specially  declares  that  "no  such  license  shall  be
construed  to  authorize  "  the  carrying  on  a  business  or  trade
"  within  any  state  or  territory  in  which  it  is  or  shall  be  spec-
ially prohibited  by  the  laws  thereof,  or  in  violation  of  the  laws
of  any  state  or  territory."  In  McGuire  v.  The  Common-
wealth,^ the  Supreme  Court  held,  under  this  section  of  the
law  of  Congress,  that  a  person  licensed  to  sell  liquors  in  Mas-
sachusetts, was  still  controlled  by  the  prohibitory  legislation  of
that  state ;  although  a  strong  attempt  was  made  at  the  bar  to
convince  the  court  that  these  provisions  of  the  revenue  law
were  repugnant  to  the  rest  of  the  act,  were  unconstitutional
and  void.     The  same  doctrine  has  since  been  reaffirmed.
n.     Express  Limitations  upon  the  Power  of  the  States  to  Tax.
§  307.  We  are  now  to  examine  the  effect  of  those  express
restrictions  upon  the  taxing  power  of  the  states,  -contained  in
the  Constitution.  States  may  levy  and  collect  no  duties  upon
imports  or  exports,  except  such  as  are  absolutely  necessary  for
the  execution  of  their  inspection  laws,  and  no  tonnage  duties.
