The brief is available here. (H/t) An excerpt:
Overruling Slaughter-House and its progeny, and overturning the settled law governing the application of the first eight amendments to the States, should require an overwhelming justification. Petitioners’ position was rejected by the post-Civil War Justices, who were in the best position to understand the meaning of the Privileges or Immunities Clause. Far from showing that the Court that decided Slaughter-House and its progeny was mistaken, the historical record demonstrates a wide array of views, from within the halls of Congress and beyond, on the meaning of the Clause. The current scholarship on the subject reveals an equally wide divide.