Onshore wind power has become one of the most important technologies for renewable electricity production throughout the world, with Germany being one of the global leaders. More than 27,000 wind turbines are currently spinning across Germany. Given the government’s ambitious renewable energy targets, their numbers will continue to rise rapidly. It has now become technically and economically feasible to install wind turbines in forested areas. Our interdisciplinary analysis combines legal knowledge with spatial land use and wind power data to analyse the past development of wind farms in German forests and check whether the existing planning instruments successfully steer their spatial distribution. Our results reveal that, since 2011, a growing number of wind turbines are being installed in forests, even if they only account for 5.5% of the total number (8% of the total installed wind power capacity) and are almost exclusively limited to six of the 16 federal states. As there are no nationwide, uniform regulations governing wind turbines in forested areas, the federal states developed their own specific regulations. While some, especially those with high forest shares, generally permit wind farms in forests for reaching their renewable energy targets, others aim to keep their forests clear. So far, planning law and regional planning could successfully steer the hitherto comparatively slow expansion of wind energy in forest areas and ensure that windmills in forests are by no means “outlaws”.