In the realm of UCL jurisprudence, Cel-Tech Communications, Inc. v. Los Angeles Cellular Telephone Co., 20 Cal. 4th 163 (1999) is a major decision, cited for numerous propositions, including the broad scope of the UCL. But Cel-Tech is also cited for something known as the "safe harbor" rule.   Under the "safe harbor" rule as enunciated in Cel-Tech, if the Legislature expressly declares conduct to be "lawful," or expressly forbids a claim for certain conduct, then that conduct falls within a "safe harbor" where no UCL claim may be asserted.  Cel-Tech, at 182.

In Lopez v. Nissan North America, Inc. (Dec. 5, 2011), the Court of Appeal (Second Appellate District, Division Four) considered a trial court decision granting summary judgment in a case alleging that Nissan calibrated odometers to over-register miles driven by at least two percent.  Nissan moved for summary judgment, arguing that California law considers an automobile odometer  "correct" if it registers the actual mileage within a tolerance of plus or minus four percent (Bus. & Prof. Code § 12500(c)).  The trial court granted summary judgment for Nissan, concluding that California's "safe harbor" provision – section 12500(c) – does not protect manufacturers from liability for intentional miscalibration, but that plaintiffs failed to raise a triable issue as to whether Nissan had deliberately designed its odometers to overregister mileage.

The Court of Appeal agreed, holding:

We hold that passenger vehicle odometers are "correct" if they register actual mileage within the four percent tolerance and the designer or manufacturer does not deliberately miscalibrate them to underregister or overregister mileage. This standard is substantially the same as that applied by the trial court in granting summary judgment for Nissan.

Slip op., at 2.  The Court found section 12500(c) to be a "safe harbor" provision, provided that intentional miscalibration was not demonstrated.  Explaining itself, the Court said:

Similarly, we conclude that section 12500, subdivision (c) provides a safe harbor against UCL claims complaining about the accuracy of odometers that qualify as “correct” under that provision. (§ 12500, subd. (c); Cel-Tech, supra, 20 Cal.4th at p. 183.) California law specifically permits a slight measure of inaccuracy in odometers because it is uniformly understood that “errorless value or performance of mechanical equipment [including odometers] is unattainable.” (NIST Handbook, Appx. A, § 2.1.) Just as “[n]o law generally requires a manufacturer to use the most expensive or most durable materials in the manufacture of its products” (Bardin v. DaimlerChrysler Corp. (2006) 136 Cal.App.4th 1255, 1273), neither the UCL nor any other law requires Nissan to employ the most accurate possible odometer design. (See Alvarez, supra, 656 F.3d at p. 935.) With respect to an odometer that qualifies as “correct” even though it may not be 100 percent accurate, the Legislature has implicitly determined that any slight injury to consumers does not outweigh the harm if more stringent requirements for precision were to apply. In deeming qualifying odometers “correct,” section 12500, subdivision (c) “clearly permit[s]” their design (CelTech, supra, 20 Cal.4th at p. 183), and we “may not use the unfair competition law to condemn actions the Legislature permits.” (Id. at p. 184.)

Slip op., at 25.

There are many pages of discussion about the evidence in the case.  Had the plaintiffs established an intentional miscalibration, it would have been a different game.   But they didn't, at least to any court's satisfaction.  Not much to say beyond that.