What if they don't have ACTVT '01' for the debugger and only '02' for their own packages?
Then they must write and F8 a new program which edits the protected one, so it can be caught in the ABAP Editor exit.
Force them to make noise and use alerts on the syslog to make noise... :-)
If developers read code and comments which tells them to bugger off then they don't voluntarily go looking for trouble IMO.
Or we can dig deeper than ACTVT '01' to make noise....
Noise for (bad) developers is better than prevention.
Cheers,
Julius