diff --git a/CMakeLists.txt b/CMakeLists.txt
index b8e58472ff..66c8b35327 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -170,6 +170,9 @@ foreach(dir examples include source test tools)
 endforeach()
 file(GLOB_RECURSE format_src ${format_glob})
 
+# check for licence
+VerifyLicence(${format_src})
+
 # Add code formatter target
 add_custom_target(cppformat)
 
diff --git a/cmake/helpers.cmake b/cmake/helpers.cmake
index f355592370..e647576e88 100644
--- a/cmake/helpers.cmake
+++ b/cmake/helpers.cmake
@@ -128,3 +128,14 @@ function(FetchContentSparse_Declare name GIT_REPOSITORY GIT_TAG GIT_DIR)
         WORKING_DIRECTORY ${content-build-dir})
     FetchContent_Declare(${name} SOURCE_DIR ${content-build-dir}/${GIT_DIR})
 endfunction()
+
+
+# Checks that every input file includes an appropriate license notice.
+function(VerifyLicence)
+    foreach(file ${ARGN})
+        file(READ ${file} file_contents LIMIT 300)
+        if(NOT "${file_contents}" MATCHES "SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception")
+            message(FATAL_ERROR "${file} does not contain an appropriate license comment.")
+        endif()
+    endforeach()
+endfunction()