Workers who fill customer orders for Internet retailer Amazon might be out of luck in their quest to be paid for time they spend going through security checkpoints each day.

Several Supreme Court justices expressed doubts Wednesday during arguments over whether federal law entitles workers to compensation for security measures to prevent employee theft.

The case is being watched closely by business groups concerned that employers could be liable for billions of dollars in retroactive pay for security check procedures that have become routine in retail and other industries.

Workers have battled for decades with employers over what tasks they should or shouldn't be paid for. The Supreme Court has previously ruled that workers must be paid for time putting on protective gear for work, but not for time waiting to take it off. And the court has found that butchers deserve to be paid for time sharpening their knives, which are essential to working at a meatpacking plant.

The latest dispute involves two former workers at a Nevada warehouse who say their employer, Integrity Staffing Solutions, Inc., made them to wait up to 25 minutes in security lines at the end of every shift. Integrity provides staffers for Amazon warehouses.

Amazon spokeswoman Kelly Cheeseman says the company's data shows that warehouse employees walk through security screenings "with little or no wait."

A federal appeals court ruled last year that the workers, Jesse Busk and Laurie Castro, deserved to be paid because the anti-theft screenings were necessary to the primary work performed by warehouse workers and it was done for the employer's benefit.