If you try to go to this page: https://docs.microsoft.com/en-us/dotnet/api/system.io.directoryinfo.setaccesscontrol?view=netcore-3.0 You get redirected to the .NET Framework 4.8 version, even though the API exists in 3.0. Here's the API in CoreFX, it's public: https://github.com/dotnet/corefx/blob/226f57b4f2bf91822604aa73338070c601d7a0fe/src/System.IO.FileSystem.AccessControl/src/System/IO/FileSystemAclExtensions.cs#L23 I think this is a bug in Docs, @mairaw. Maybe a problem with mdoc when reflecting on the ref assemblies?