President Barack Obama on July 29 signed S. 754, which directs the Secretary of Agriculture to establish a national mandatory bioengineered food disclosure standard.

The law nullifies the Vermont mandatory G.M.O. labeling law that took effect July 1. The law requires food manufacturers to disclose the presence of bioengineered ingredients in one of three ways: text on the package, a symbol on the package or a link to a web site (a quick response code or similar technology).

Many in the food industry support the law.

“This legislation will open a new era for transparency in ingredient information for consumers, by requiring disclosure of genetically engineered ingredients for families in every state across the nation,” said Pamela G. Bailey, president and chief executive officer of the Washington-based Grocery Manufacturers Association. “Its consistent national standard is far better than a costly and confusing patchwork of different state labeling. The president’s signing of this legislation also stops, effective immediately, Vermont’s mandatory on-package labeling law that went into effect July 1 and already has left consumers in the state with fewer products on the shelves and higher compliance costs for small businesses.”

Gary Hirshberg, chairman of Just Label It and co-founder of Stonyfield Farm, Londonderry, N.H., urged food companies to go with the option of putting “clear and simple” labels on their products.

“Consumers have already begun to see G.M.O. labeling disclosures on many familiar food packages as companies prepared to comply with Vermont’s groundbreaking law,” he said. “In the wake of the creation of a national, mandatory labeling system, Campbell’s, Mars and Dannon have already publicly committed to keeping this simple disclosure on their packages as U.S.D.A. sorts out the rules for implementation of this new law. I have sent a letter to other industry leaders asking them to publicly commit to keeping consumers out of the dark when it comes to G.M.O.s in our food.”