The trial court abused its discretion in holding that environmental protection parties were not entitled to attorney fees against a homeowner’s association under CCP 1021.5 under the Adoption of Joshua S. (2008) 42 Cal.4th 945 exception. That exception is narrow; it applies only to parties that litigate purely private matters that happen to raise issues of public importance. It does not apply when a party’s suit adversely affects the public interest which the fee applicant successfully defends. So, in this case, the association’s suit to overturn a prior settlement that re-routed a highway extension near the association’s properties and away from an environmentally fragile area was a suit that adversely affected the public interest that the environmental protection parties then successfully defended. The association’s suit infringed the public interest, and thus the Joshua S. exception didn’t apply.