A federal judge is weighing whether to put the brakes on Vermont's first-in-the-nation GMO labeling law before it even goes into effect.

Judge Christina Reiss had probing questions for both sides in the lawsuit that the Grocery Manufacturers Association filed against the state of Vermont. She held a hearing Wednesday in federal court in Burlington.

Reiss heard arguments from the state concerning its motion to dismiss the lawsuit, and from the association regarding its request for the court to suspend the labeling law while considering whether the measure is constitutional.

The Vermont law would require that processed foods made entirely or partially with genetic engineering be labeled "produced with genetic engineering," or "partially produced with genetic engineering" or "may be produced with genetic engineering."

The judge focused on the last iteration of the labeling requirement, pressing a private attorney representing the state, Larry Robbins of the Robbins Russell law firm in Washington, D.C., about the value of a law that would allow manufacturers to say only that their products "may be produced with genetic engineering."

Why, she asked, would manufacturers go to the trouble and expense of determining whether their products have genetically engineered ingredients when they could just "slap on a label" saying they "may" contain GMOs?

Given that possibility, Reiss questioned the value of labels that tell consumers something they already know, given that it is generally accepted that 90 percent of the corn and large percentages of other commodity crops in the United States are grown with genetically engineered seeds.