How do I handle players who won't follow the rules?

Distinguish between forgetfulness and defiance
Most rule-breaking is accidental. Someone forgot a restriction, misunderstood a mechanic, or got confused. Clarify gently: "Actually, you can only do that if..." as a reminder, not an accusation.
Pause and check together
When unsure if something's allowed, stop and look it up. This takes 30 seconds and prevents 10 minutes of incorrect play. Use the rulebook as referee, not the adult's memory.
Set expectations before play
Before starting, agree that everyone will follow written rules. Explain that rules exist to keep things fair and predictable. Kids understand fairness; frame it that way.
Distinguish house rules from cheating
House rules (intentional changes agreed before play) are fine. Mid-game invention to gain advantage isn't. If someone wants to change a rule, pause the game, discuss it, and agree together before resuming.
Restart if necessary
If rule-breaking escalates or feels intentional, stop and restart. Say clearly: "We need to play by the written rules, or we can't finish fairly." Don't shame; just reset.
Accept that young kids need scaffolding
Under age 7, rules breaking is normal—impulse control is developing. Gentle reminders work; punishment doesn't.