The ban is currently making headlines in Wisconsin, with local media outlets reporting on how “regulation madness” had been “forcing ‘illegal butter’ off store shelves” and one commenting: “I can’t believe it’s not legal.”

"Under Wisconsin legislation, retail butter for sale in Wisconsin must bear either a Wisconsin or federal grade mark. This effectively excludes Kerrygold butter being sold in Wisconsin because Kerrygold butter is graded, produced and packaged in Ireland," Ornua told the Irish Farmers Journal in a statement on Wednesday.

While this was not enforced in the past, local authorities have recently revived the grading obligation. Ornua made a first public mention of the ban in April 2015 in social media interactions with customers finding it harder to buy Kerrygold butter.

Ornua added that no other states were affected.

It is only in recent days that a blanket ban has come into force in application of the 1970s legislation, with stores facing fines for stocking the flagship Irish butter. This has prompted consumers to take to social media again and exchange addresses of retailers defying the prohibition or tips to order Kerrygold online. Others said they were driving to neighbouring states to constitute stockpiles.

Some were quick to notice that Wisconsin happens to be the leading dairy producer in the US, giving the revival of old consumer protection law a whiff of protectionism. The state has largely contributed to the ongoing US dairy expansion.

"We are currently working with the Wisconsin authorities on a solution which will enable consumers throughout the state enjoy the great taste of Kerrygold butter," Ornua's statement said.

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