Online retailer Amazon.com, criticized for not acting quickly enough to curb sellers who charged hundreds of dollars for high-demand hand sanitizer during the early phase of the new coronavirus pandemic, urged Congress on Wednesday to pass a law against price gouging during times of national emergency.

Price-gouging is not usually illegal but can be in certain states if there is an emergency, like during a hurricane or the current pandemic.

In a blog post, Brian Huseman, a vice president of public policy at Amazon, noted that different states had different definitions of gouging and that some fight gouging using consumer-protection statutes.

“The disparate standards among states present a significant challenge for retailers working to assist law enforcement, protect consumers, and comply with the law,” Huseman wrote.

A group of 32 U.S. state attorneys general wrote to Amazon in March, and to Walmart Inc., Facebook Inc. and eBay Inc., urging that they did more to stop gouging. In March, some sellers on Amazon notoriously charged $400, or more, for a box of small bottles of Purell hand sanitizer.

In response to the price-gouging criticism, Huseman said Amazon had removed more than a half million items from stores, suspended nearly 4,000 selling accounts in the U.S. store, and given information to federal prosecutors and state attorneys about sellers that Amazon suspects put excessively high prices on products in high demand because of the coronavirus pandemic.

Huseman argued for a law that would come into force if a national emergency is declared, be enforced by the Federal Trade Commission and the states, and which would define gouging.