What makes a merger? It was a question asked often last year, thanks to a trio of transatlantic tie-ups in which law firms joined forces but kept their finances separate via a Swiss structure called the verein. Hogan Lovells, SNR Denton, and Squire Sanders & Dempsey, which kept that name after combining with Hammonds, joined global giants Baker & McKenzie and DLA Piper in operating under vereins , as did U.K. firm Norton Rose, which used the verein in teaming with firms in Australia, Canada, and South Africa.

Critics say that using the verein —which, simply put, is a holding structure that lets participating entities maintain their existing forms—makes these unions less than true mergers. K&L Gates chairman Peter Kalis, for instance, labeled them “Noah’s Ark” mergers because of the lack of total financial integration, saying, “A merger is when two become one, not when two become two.”