こんな感じですかね？
exists([Type == "http://schemas.microsoft.com/2012/01/requestcontext/claims/x-ms-proxy"])
&& NOT exists([Type == "http://schemas.microsoft.com/2012/01/requestcontext/claims/x-ms-endpoint-absolute-path", Value == "/adfs/ls/"])
=> issue(Type = "http://schemas.microsoft.com/authorization/claims/deny", Value = "true");