Riparian vegetation plays a key role in maintaining biodiversity and ecosystem services, and in Brazil it is legally protected as Permanent Preservation Areas (PPA) under the Native Vegetation Protection Law (Law 12,651/2012). However, the definition of riparian PPA widths has changed over time, creating challenges for environmental management and regularization. In this study, we analyzed land use and land cover dynamics in riparian PPA of São Paulo State, Brazil, comparing conditions in 1985, under the 1965 Forest Code (Law 4,771/1965), and in 2022, under the current legislation. We assessed the effects of legal changes, land use transitions, and the principle of temporality applied by the state environmental agency, which allows regularization of anthropic uses established before 1986. We used geoprocessing and spatial statistics to identify land use dynamics and clusters of maintenance, suppression, and regeneration of native vegetation in PPAs. In 1985, agriculture and forestry dominated these PPA areas (54%), while in 2022 forest and natural formations became predominant (49%). The most relevant land use transition was the regeneration of native vegetation from pastures, totaling 262,297 ha. Anthropic areas increased by 113%, concentrated in the São Paulo metropolitan region. Of these, 11,654 ha (0.4% of total PPA) were already occupied in 1985 and may be considered regular under the temporality principle (i.e. not in conflict with legislation). Our results suggests that legal expansion of PPA widths after 1986 contributed to natural regeneration, particularly in southern and northeastern regions of the state, but agricultural uses remain the main drivers of riparian degradation. The integration of geospatial analyses with legal frameworks offers critical support for management, enforcement, and the design of incentive-based policies to promote restoration beyond minimum legal requirements.