Mr. Ji and his peers have used these laws to their advantage, buying knockoffs in bulk — the more they turn in, the more they are paid — and filling their storerooms withcounterfeit products. Mr. Ji’s group, the Jinan Old Ji Anti-Counterfeit Rights Defense Work Studio, has a network of about 20 informers who report suspected fake products. He says his biggest success to date is collecting about $178,000 in compensation from a company that tried to pass off its blankets as pure cashmere.

China’s e-commerce boom has given counterfeit hunters a new front.

“The main purpose of suing them is to ask them to correct themselves,” said Yu Fengxing, another counterfeit hunter, who chases merchants who sell fakes on online marketplaces run by the Alibaba Group, China’s largest e-commerce company. He became an e-commerce counterfeit hunter after he bought an item marketed by a merchant on Alibaba’s Tmall platform as a foot treatment and discovered that it was probably just makeup. In a statement, Alibaba said it was committed to fighting fakes on its platforms.

Among overseas companies, people like Mr. Ji have fans. “A lot of my clients would, in some circumstances, support the activities of these kinds of consumer warriors because ultimately they may be uncovering information that helps us do our job,” said Scott Palmer, an intellectual property lawyer at Sheppard, Mullin, Richter & Hampton, which represents American corporations in China.

But government officials complain that the program is increasingly expensive and increasingly abused. Even some foreign business groups complain. Counterfeit hunters often profit “from complaints that target minor product labeling errors instead of true quality or safety issues,” said James Zimmerman, chairman of the American Chamber of Commerce in China, in emailed comments.

Image Lamborghini smartphones falsely labeled as being made in Switzerland. Even as China grows and matures, and moves to protect brands and ideas, it still struggles with how to get rid of fakes. Credit... Gilles Sabrié for The New York Times

Proposed government rules released in August and under official consideration said that payouts for fakes would not be available to those who sought them “for commercial purposes.”

Mr. Ji, defending his work, says he has to recoup his legal fees, which he incurs when the companies he accuses of selling fakes fight back. He says he makes about $148,000 a year but his take-home pay is only about $30,000 to $44,000 after expenses.