Define a rule, announce it to people, educate them if needed on the subject, monitor and reward those, who obey the rule, establish consequences for violating it, establish a reporting mechanism, evaluate and improve at any step if something is not working.
The way you enforce any rule.
So, how do you enforce any rule?
Define a rule, announce it to people, educate them if needed on the subject, monitor and reward those, who obey the rule, establish consequences for violating it, establish a reporting mechanism, evaluate and improve at any step if something is not working.