Are there national rules on playing up an age category?

Ringette Canada's published policies do not set a general playing-up rule for U16 or U19. What they do say:

• Competition age categories follow the Registration and Eligibility Policy (age as of December 31 of the playing season), unless the competition's Technical Package specifically says otherwise (Competitions Policy, section 8).
• Ringette Canada's older Athlete Registration, Eligibility and Transfer Policy (last reviewed November 2013) said exceptions to the age categories may be permitted by the Board, at its sole discretion, on a written request. The current web version of the policy (last reviewed March 2020) does not include that wording.