This section is from the book "The Law Of Contracts", by William Herbert Page. Also available from Amazon: Commercial Contracts: A Practical Guide to Deals, Contracts, Agreements and Promises.
It is impracticable and impossible to set forth in writing all the different stipulations and provisions which, by the operation of law, are terms of the contract. The difficulty exists, not because the contract is in writing, but because it is impossible to make an exhaustive enumeration in express words of everything which may in law be a part of the contract. Some things are a part of the contract which are in the minds of both parties, though not stated in express languages. Other things are presumed to be in the minds of the parties; but in many cases this presumption is purely artificial - a mere fiction. What is really meant is that certain things affect the contract, even if the parties do not agree upon them or even think of them. Valid laws which are in force when the contract is made are a part thereof, even though not expressly referred to.1 Thus an ordinance requiring the walls of opera-houses to be of a specified thickness is a part of a contract of subscription for the erection of an opera-house within the city, although it is not referred to therein.2 So municipal ordinances creating and establishing fire limits are part of a contract of insurance of property in such limits, and bind the insurer.3 An unconstitutional statute is not, however, a term of a contract made between the time that it is passed and the time that it is declared unconstitutional;4 even, it has been held, if expressly made a part of the contract.5
1 Summers v. Hibbard, 153 I1l. 102; 46 Am. St. Rep. 872; 38 N. E. 899.
2 Sturm v. Boker, 150 U. S. 312.
3 Pemberton v. Dean, 88 Minn. 60; 97 Am. St. Rep. 503; 60 L. R. A. 311; 92 N. W. 478.
1 Nielsen v. Assurance Society, 139 Cal. 332; 96 Am. St. Rep. 146; 73 Pac. 168.
2Gerner v. Church, 43 Neb. 690; 62 N. W. 51.