To anyone opposed to any law requiring the labeling of foods containing bioengineered ingredients, disappointment rules over a law passed by both houses of Congress this month. After all, the law does indeed require labeling of such ingredients, either in plain print on the package label or with a Q.R. code readable by smartphones. To many, requiring listing of ingredients yet to be proven harmful to health is anathema. The inclination to recoil at such laws has intensified as evidence mounts sky high that bioengineered crops pose absolutely no risks.

Still, any disappointment is mollified by comments like the following from a very different opponent of the new proposed law. “This is not a labeling bill; it is a non-labeling bill,” said Andrew Kimbrell, executive director of the Center for Food Safety. “Clear, on-package G.E. food labeling should be mandatory.” In a rare display of genuine compromise, Congress approved a federal law preempting a Vermont law that would have required exactly the kind of labeling advocated by Mr. Kimbrell.

Still, it is far from clear his assessment is accurate. Whether food companies will embrace the Q.R. code option, which informs consumers motivated to learn about bioengineered ingredients, remains to be seen. Regardless of scientific merit, the momentum and clout gained by advocates of mandatory labeling are considerable. Numerous food companies have buckled under pressure to proactively embrace labeling. To the degree labeling becomes the norm, it may be difficult for many companies to resist quiet conformity, with clear labeling turning out to be the safest course.