Article I, Section 10, Clause 1:
No State shall enter into any Treaty, Alliance, or Confederation; grant Letters of Marque and Reprisal; coin Money; emit Bills of Credit; make any Thing but gold and silver Coin a Tender in Payment of Debts; pass any Bill of Attainder, ex post facto Law, or Law impairing the Obligation of Contracts, or grant any Title of Nobility.
The police power, too, has frequently benefitted from the doctrine of strict construction, although this recourse is today seldom, if ever, necessary in this connection. Some of the more striking cases may be briefly summarized. The provision in the charter of a railway company permitting it to set reasonable charges still left the legislature free to determine what charges were reasonable. 1 However, when a railway agreed to accept certain rates for a specified period, it thereby foreclosed the question of the reasonableness of such rates. 2 The grant to a company of the right to supply a city with water for twenty-five years was held not to prevent a similar concession to another company by the same city. 3 The promise by a city in the charter of a water company not to make a similar grant to any other person or corporation was held not to prevent the city itself from engaging in the business. 4 A municipal concession to a water company to run for thirty years, and accompanied by the provision that the
said company shall charge the following rates, was held not to prevent the city from reducing such rates. 5 But more broadly, the grant to a municipality of the power to regulate the charges of public service companies was held not to bestow the right to contract away this power. 6 Indeed, any claim by a private corporation that it received the ratemaking power from a municipality must survive a two-fold challenge: first, as to the right of the municipality under its charter to make such a grant, secondly, as to whether it has actually done so, and in both respects an affirmative answer must be based on express words and not on implication. 7