Photo courtesy of Shannon Hutchison
Today's rule interpretation
You can play 3 in when you're short
Offensively...
When your team is serving more than 1 penalty, the rules require that at least 1 skater remain outside of your defending zone restricted area.
However, when you are in your attacking zone, attempting to score a goal - you may have all 3 skaters enter that zone.
Ringette Canada Official Rules

