How to lock cpu priority of a process and block it from changing the priority itself?

I have an application that is programmed to change it’s priority to high. Even if I switch it back to normal or lower, it changes back after some time. How can I block this behavior? How can I force process’ cpu priority so that it can’t change the priority itself? The closest solution I’ve come to so far was a script that checks the priority and changes it if necessary, however this solution doesn’t force the priority for all the time.