Japan's ban on the price-gouging resale of face masks came into force on Sunday. Tokyo took the measure as masks have been in short supply amid the coronavirus outbreak.
Violators will face penalties of up to one year in prison or a fine as high as about 9,500 dollars.
The legislation bans the resale of masks by individuals and companies at prices higher than the cost of buying them at retailers or elsewhere. The measure applies to sales on online auctions as well.
The ban is based on the 1973 Act on Emergency Measures for Stabilization of National Life that was enacted in response to the global oil crisis. The law has never been invoked for nearly five decades.
The government has provided subsidies to mask makers to help boost production. It says it has secured a supply of more than 600 million masks a month, including imports.
But it would be far from enough to meet the growing demand.