It depends if they are exempt or non-exempt (from the FMLA). Generally, hourly workers are non-exempt and salaried exempt, but there can also be salaried non-exempt or hourly exempt.

If they are exempt, they don't have any limits on how long they can work. If non-exempt, they must be paid overtime (generally 1.5x their wage) above 40 hours/week. If they aren't being compensated for overtime, they can file a complaint with the Attorney General. I'd also advise they consult an labor attorney.

Alternatively, if your friend is covered by a union, he should consult with their union rep. Their contract may have protections in place.