For convenience, the API functions that specify a handle to the security policy file (except for secpol_close()) allow you to specify NULL for handle.
If you are calling multiple functions, you can first call secpol_open(NULL, SECPOL_USE_AS_DEFAULT), which specifies that the system's default security policy file is used and that file is used when handle is NULL for the subsequent functions.
When you call a single function, you can omit a call to secpol_open() that sets a default security policy. Instead, set handle for the function to NULL, which will specify the default system security policy file.