MADISON, Wis. (AP) — In butter-loving Wisconsin, a ban on Irish butter has sparked a fight.

A handful of Wisconsin residents has filed a lawsuit challenging a 1953 state law that bans the sale of Kerrygold Irish butter, or any other butter that hasn't been graded for quality.

Tired of trekking across state lines to stock up, the plaintiffs say it's unconstitutional to require that all butter sold in Wisconsin undergo a "government-mandated 'taste test.'" Wisconsin is the only state with such a stringent rule.

The Wisconsin Institute for Law and Liberty is representing the plaintiffs. The conservative legal group says the issue is one of economic liberty, not consumer safety.

The lawsuit was filed against the Wisconsin Department of Agriculture, Trade and Consumer Protection. The agency says it has to uphold state law.