Several EU Member States argue that active afforestation of degraded peatlands should be recognized as a restoration measure under the Nature Restoration Law (NRL). In this perspective paper, we discuss the scientific evidence on the greenhouse gas fluxes of peatlands under forestry and its limitations, uncertainties and evidence gaps. In our opinion: Afforestation of drained peatlands, while maintaining their drained state, is not equivalent to ecosystem restoration. This approach will not restore the peatland ecosystem's flora, fauna, and functions. Currently, there is insufficient evidence to support the long-term climate change mitigation benefits of active afforestation of drained peatlands. Most studies only focus on the short-term gains in standing biomass and rarely explore the full life cycle emissions associated with afforestation of drained peatlands. Thus, it is unclear whether the CO2 sequestration of a forest on drained peatland can offset the carbon loss from the peat over the long term. In some ecosystems, such as abandoned or certain cutaway peatlands, afforestation may provide short-term benefits for climate change mitigation compared to taking no action. However, this approach violates the concept of sustainability by sacrificing the most space-effective carbon store of the terrestrial biosphere, the long-term peat store, for a shorter-term, less space-effective, and more vulnerable carbon store, namely tree biomass. Consequently, active afforestation of drained peatlands is not a viable option for climate mitigation under the EU Nature Restoration Law. To restore degraded peatlands, hydrological conditions must first be improved, primarily through rewetting. This paper has been supported by the WET HORIZONS project.