Under the act, the male population of Canada was divided into several classes for the purpose of being called up for military service, from which certain exceptions were available, if they were:

• ordinarily resident in Canada; or
• has been at resident in Canada at any time since August 4, 1914, unless where he
• falls within one of the specified exceptions, or he
• reaches the age of 45 prior to his class or subclass being called up.

With the classes being:

• Those who have the age of twenty years, born not earlier than 1883, and are unmarried or a widower with no child.
• Those who have the age of twenty years, born not earlier than 1883, and are married or a widower with a child or children.
• Those born in the years 1876 to 1882 inclusive, and are unmarried or a widower with no child.
• Those born in the years 1876 to 1882 inclusive, and are married or a widower with a child or children.
• Those born in the years 1872 to 1875 inclusive, and are unmarried or a widower with no child.
• Those born in the years 1872 to 1875 inclusive, and are married or a widower with a child or children.

Any man married after July 6, 1917, was deemed to be unmarried.

The exceptions to the act were:

• Men who hold a certificate of exemption issued under the act.
• Members of His Majesty’s regular, reserve or auxiliary forces.
• Members of military forces raised by any of the other Dominions or the Government of India.
• Men serving in the Royal Navy, the Royal Marines, the Naval Service of Canada or the Canadian Expeditionary Force.
• Men who have served since August 4, 1914, in the military or naval forces of Great Britain or her allies in any theatre of actual war, and have been honourably discharged.
• Clergy, members of holy orders and ministers of any religious denomination existing when the act came into force.
• Persons exempted from military service by the Orders in Council of August 13, 1873 and December 6, 1898.

And finally the exemptions were:

• Importance of continuing employment in habitual occupation.
• Importance of employment in a special occupation for which one has special qualifications.
• Importance of continuing education or training.
• Serious hardship owing to exceptional financial obligations.
• Serious hardship owing to exceptional business obligations.
• Serious hardship owing to exceptional domestic position.
• Ill health or infirmity.
• Adherence to a religious denomination of which the articles of faith forbid combatant service.