Be careful of what you might do to staff morale if you decide to strictly enforce a "you must take 30 minutes unpaid lunch every day no matter what" policy! And don't tell employees the law requires them to take 30 minute lunch if no such law exists. In my state, a 30 minute lunch period must be OFFERED to the employee and they cannot be forced to work during the break if that time is unpaid.
At my bank, some employees in busy positions (wire transfer, IT) were punching out for their lunches and eating in the cafeteria and then being called back to their duties early quite often("this wire needs to go out RIGHT NOW!" or "my PC is broken - come quick!"), sometimes resulting in less than 30 minutes clocked out for their lunch period. Management started docking these employees' paychecks for the balance of the 30 minutes (i.e. wire employee only took 26 minutes for lunch before being summoned back to work to send that all-important wire, end of the week comes, time card has "MINUS 4 minutes: short lunch Tuesday" written on it by HR). Result: angry employees who feel unappreciated (no good deed goes unpunished!) and now simply leave the bank for their lunch periods and breaks. Now, they're simply unavailable for those "emergencies" and have less helpful attitudes in general.
Be careful what you wish for, and no matter what, treat employees like human beings worthy of respect, particularly when they are shortening their lunch to help out the bank or their co-workers and NOT to try to leave early.
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"Gratitude makes sense of our past, brings peace for today, and creates a vision for tomorrow." - Melody Beattie