Historically, the law knew but substantive law, matters of procedure left to the whim of the presiding judicial officer. But over time, the courts developed rules of evidence and of procedure, which can be grouped into the term procedural law (also known as adjective law), mostly related to fairness and transparency of process.
Relying on Re Coles and Ravenshear's, the authors of the 5th edition of Halbury's laws of England (2009),
"Substantive law creates rights and obligations and determines the end of justice embodied in the law, whereas procedural law is an adjunct or an accessory to substantive law."
In Wing Construction Ltd., Justice Scott of the Manitoba Court of Appeal adopted these words:
"While the distinction between substance and procedure is not always easy to draw, it is well recognized nonetheless.
"The function of substantive law is to define, create or confer substantive legal rights or legal status or to impose and define the nature and extent of legal duties.... ;
"The function of practice and procedure is to provide the machinery or the manner in which legal rights or status and legal duties may be enforced or recognised by a court of law or other recognised or properly constituted tribunal."
In Sutt, a family law case, Justice Schroeder wrote:
"It is vitally important to keep in mind the essential distinction between substantive and procedural law.
"Substantive law creates rights and obligations and is concerned with the ends which the administration of justice seeks to attain....
"(P)rocedural law is the vehicle providing the means and instruments by which those ends are attained. It regulates the conduct of Courts and litigants in respect of the litigation itself whereas substantive law determines their conduct and relations in respect of the matters litigated."
In Ernst v. Ernst, the Ontario High Court, in 1977, defined substantive as applied to law as:
"... relating to or consisting of the rules of right administered by a Court as opposed to forms of procedure. Procedure is defined as: The mode or form of conducting judicial procedure as distinguished from those branches of law which define rights or prescribed penalties."
In Poyser v. Minors, Justice Lush, although he did not specifically use the phrase substantive law, broached the topic of the traditional distinction between procedure and substantive law:
"Practice in its larger sense - the sense in which it was obviously used in that Act, like procedure which is used in the Judicature Acts, denotes the mode of proceeding by which a legal right is enforced, as distinguished from the law which gives or defines the right, and which by means of the proceeding the Court is to administer the machinery as distinguished from its product."
In his 1932 article for the Harvard Law Review, Arnold Thurman of Yale Law School wrote:
"The distinction between procedure and substantive law is one of the most interesting consequences of our attitude toward an independent judiciary. Substantive law is sacred and fundamental. It represents the experience of the ages. On it is based the freedom of the individual. It never needs reform because its fundamental verities can always be discovered by logical analysis. Procedure, on the other hand, is entirely practical. It always needs, not logic, but change in the light of practical details. It is based on the experience of the ages also, but age with it is senility, not wisdom. Yet, in spite of these fundamental differences, no one has ever been able to formulate any test which will distinguish between procedure and substantive law in any particular case. Substantive law remains the law which we enforce, procedure the practical rules by which we enforce it. We therefore always restate substantive law in the light of its principles, and reform procedure in the light of its practical problems.
"The distinction is most useful in the judicial system, once we realize that the difference is only in attitude, that any doctrine may be treated as procedure and the problem discussed, or as substantive law and the principle stated. The difference between procedure and substantive law is a movable dividing line which may be placed wherever an objective examination of our judicial institutions indicates is necessary....
"Substantive law is canonized procedure. Procedure is unfrocked substantive law."
In their book, authors John Horn and others wrote:
"(P)rocedure exists only to give effect to substantive law, that it is the handmaiden of justice."
- Ernst v. Ernst, 4 C.P.C. 18 (1977)
- Horn, John; Fraser, Peter and Griffin, Susan, Conduct of Civil Litigation in British Columbia (Toronto: LexisNexis, 2011), page 2-1
- Poyser v. Minors,  7 Q.B.D. 329
- Re Coles and Ravenshear's Arbitration,  KB 1
- Sutt v Sutt ,  1 O.R. 169 (Ontario Court of Appeal).
- Thurman, Arnold, Role of Substantive Law and Procedure in the Legal Process, 45 Harv. L. Rev. 617 (1931-1932)
- Wing Construction Ltd. and others v Sagkeeng First Nation, 2003 MBCA 115