People who teach interference with business relations, as I at times have, and who talk about Tuttle v. Buck, 119 N.W. 946 (Minn. 1909), might want to note that Gieseke v. IDCA, Inc., 2014 WL 1230224 (Mar. 26, 2014), http://scholar.google.com/scholar_case?case=1077147170935303643, adopts the independent unlawfulness requirement: "To ensure that fair competition is not chilled, a claim for tortious interference with prospective economic advantage must be limited to those circumstances in which the interference is intentional and independently tortious or unlawful, rather than merely unfair." “[This] requirement of independently tortious or unlawful conduct adequately apprises potential defendants of the conduct that will subject them to liability.” “[The elements of the tort include t]hat defendant intentionally interfered with plaintiff's reasonable expectation of economic advantage, and the intentional interference is either independently tortious or in violation of a state of federal statute or regulation." 

 

The Gieseke court doesn’t say that Tuttle v. Buck is overruled, and cites it positively (though recharacterizing it as simply involving “threats, false reports, and accusations against the plaintiff”).  But the Gieseke holding seems to reject Tuttle’s broader approach.