Canadian Federal Court Justice W. Andrew McKay has ruled that Infiniti can't use the letter M to name its cars in a manner similar to BMW's already-existing naming conventions, and that its usage "in form similar to that of the plaintiffs' trademark M alone, and its use of M6 as a package for modifying one of its vehicles, cause confusion in Canada between the sources of the wares of the defendant and the wares of the plaintiffs."
True, Infiniti does not make a vehicle called the M6, which BMW does, but the company does offer an "M6" option on the G35 sports sedan. BMW apparently thinks that Infiniti buyers might think they're getting a Bavarian-engineered option on a Japanese car, and had their lawyers pounce on Nissan's luxo-brand.
BMW has been adding "M" to its model nomenclature since 1978 in Germany (and 1987 in Canada) to denote high-performance sedans, such as the M3, the M5, and the M6. Infiniti makes the M35 and M45 mid-range sedans, and in some advertising just talks about the "M" cars with just that one letter. The use of M6 to stand for an option package is found just on the G35, mentioned above.
Mr. Justice McKay found that Infiniti's parent company, Nissan, was "liable, in damages to be determined . . . for the use of the letter M and the descriptor M6, as trademarks for automobiles, parts and accessories, which caused a likelihood of confusion between the sources of its wares and of BMW's." He ordered that any materials which feature the name in question that might cause confusion between Infiniti and BMW in the minds of consumers be either rounded up and delivered to BMW, or destroyed under oath.
Source: CBC