You should conform to the rules.
You should keep to the regulations.
You must keep to the rules.
You must conform to the rules.
You should obey those rules.
You must act in accordance with the rules.
You must follow the regulations.
You must keep to the regulations.
You must follow the rules.
You must observe the rules.
You should follow this rule.
You must respect that rule.
You must observe those rules.
We must conform to the rules.