As they re-entered in December, they have valid status until June.You can apply for restoration of status (to visitor status) as long as you apply within 90 days of the refusal.
I am not sure what that bit means about "person in immigration legislation".
You were not issued a removal order just a refusal and while you are technically now in Canada "illegally" you don't have to pack up and leave. Submit the restoration application and wait it out. Mine took just under 3 months.
You are currently out of status.
If you are refused restoration you must then leave.