Thanks for your posting. This is currently not supported but if you are concerned about moving test cases from one test suite to another you can disable this by removing the Delete permissions for Test Cases & Sections. As moving a test case from one suite to another may also delete associated test results in active test runs, this can be denied by removing the Delete permissions. Moving test cases in the same test suite is still possible even with removing the Delete permissions.
I hope this helps and please let me know in case you have any further questions.