Mandatory Overtime Definition
Mandatory overtime is when employers require employees to work in excess of 40 hours per workweek, even if employees don't want to. Subsequently, employees often refer to it as forced mandatory overtime or simply forced overtime.
Mandatory Overtime Law
There is no Federal mandatory overtime law per se, that specifically regulates so-called forced overtime. The only Federal "overtime law" is under the Fair Labor Standards Act (FLSA), which also regulates equal pay, child labor and the minimum wage.
Mandatory Overtime under the FLSA
Federal overtime law under the FLSA does not prohibit employers from forcing employees to work mandatory overtime.
In fact, the FLSA doesn't at all restrict the total number of work hours that employers may schedule for employees who are age 16 or older. The FLSA restricts work hours only for employees who are younger than age 16.
In other words, there are no protections under the FLSA for workers 16 and older who refuse to work mandatory overtime. As a result, workers 16 and older who refuse to work it are "legally" subject to employer discipline, up to and including discharge.
Under FLSA overtime law (exclusive of child-labor provisions), total daily and weekly work hours are a matter of contractual agreement between employers and employees or employers and unions. In the absence of contractual agreements that restrict work hours (such as collective bargaining agreements), employers may effectively force employees to work any number of mandatory overtime hours within reason.
If you are protected by the Americans with Disabilities Act (ADA) or Rehabilitation Act, then your employer might be required to modify your mandatory overtime schedule to reasonably accommodate your disability.
Without union representation (or a potential disability protection mentioned above) and outside of filing a lawsuit, negotiating one-on-one or through your attorney is likely to be the only "legal" way to convince your employer to reduce your mandatory overtime work hours. If that fails, then you'll likely have little choice but to involuntarily work the forced overtime or quit for a better job.
The state (or municipality) in which you work might have enacted its own overtime law, that has more generous employee provisions than the FLSA. However, it's not likely to restrict the number of mandatory overtime hours for all workers. To find out, start by checking with the relevant state labor department or consult an attorney.
Mandatory Overtime Lawsuits
Employers can't always get away with forcing mandatory overtime, such as by "squeezing" current workers to avoid hiring new workers. Employee lawsuits against employers regarding excessive mandatory overtime are on the rise, particularly by salaried-exempt employees.
Because salaried-exempt employees are not eligible for overtime pay under the FLSA, employers may require them to work extra hours without extra pay. Even so, when forced, excessive work hours became the "norm" every workweek, some salaried-exempt employees filed and won so-called mandatory overtime lawsuits.
Consult an attorney about challenging your employer's forcing of excessive mandatory overtime, through a lawsuit. Overtime lawsuits are often class actions.
In contract negotiations, union workers too have won mandatory overtime concessions; for example, when employers forced it to avoid hiring new union workers. Consult your union rep about that.
The U.S. Occupational Safety and Health Administration (OSHA) published a Safety and Health Guide entitled "Extended/Unusual Work Shifts". It recommends that employers grant extra meal and rest breaks when work shifts exceed eight hours per day; but, it's only a guide with no legal teeth.