Newly installed biometric facial recognition scanners at Washington Dulles International Airport in Deptember 2018. (Bill O'Leary/The Washington Post)

AND THEN there were three. Amazon has joined Microsoft and Google in supporting regulation of facial recognition technology, and it is easy to guess why: Research on bias in the software has amplified public skepticism, and legislators are starting to take note by proposing restrictions and even bans.

Facial recognition technology could have many beneficial effects. The software could help stop human trafficking, reunify refugee families and make everyday services — from banking to paying for groceries — safer and faster. But it could come with costs, too, which is why regulators are right to pay attention. There is currently no federal standard on facial recognition, so Congress should step in.

The first problems to tackle are potential bias and inaccuracy. Amazon, whose founder and chief executive, Jeffrey P. Bezos, also owns The Post, has disputed the results of studies claiming its software performs worse at identifying darker-skinned individuals and all women. The stakes are obvious, especially when it comes to law enforcement use of recognition technology. Already, police in Baltimore have run protesters’ faces through recognition software against mug shot repositories “for the purposes of trying to identify those who were involved in criminal wrongdoing.”

Lawmakers should mandate an external review system that tests recognition technologies not only in the lab, but also in the field. They should then require that governments only use tools that meet a high accuracy threshold, and set those tools to reveal results only with a high confidence score. Anyone who is arrested based on a recognition algorithm should also be informed how that system performs across demographics.

Those remedies for discrimination should fit into a broader regime governing the proper use of recognition software. There’s precedent to look to on other technologies, from wiretapping to location gathering via cell tower. Running someone’s face against a mug shot database should require probable cause; continuous tracking of a suspect from camera to camera should occur only with a warrant. Real-time face scanning by cameras across a city of every passerby should be limited to public emergencies.

Private actors’ harnessing of recognition technology will also require attention. There seems to be broad agreement that businesses should notify consumers if they run recognition on their websites or premises, but Congress will have to figure out what constitutes meaningful consent to face-collection as well as what limits to impose on processing and sharing.

Prudent regulation would tilt the competitive field toward companies that are acting responsibly. If companies don’t do recognition right, customers will look elsewhere, because they won’t be allowed to buy. Slow, steady and safe should win this race.