At issue were fees paid to the state of Illinois by the railroad company. Illinois charged the railway more money to transport goods to a close destination then it did a farther one. The supreme court had no issue with fees charged within the Illinois border.
The 1886 Wabash, St. Louis & Pacific Railway Company vs. Illinois overturned a previous case that allowed states to regulate railroads. Illinois wanted the right to charge the transportation company for their portion of its journey.
Constitutional Question: Should the states regulate commerce beyond their state boundaries?
The Supreme Court declared that states could NOT regulate commerce that went beyond their boundaries. Instead, regulation had to come from the federal government.
The case asserted the Constitutions authority that the federal government regulates interstate commerce and not the states.