SUBSYSTEM=="block", RUN="/sbin/program" will execute the program only for block device events. ACTION="remove", SUBSYSTEM=="block", RUN"/sbin/program" will execute the program, if a block device is removed.
SUBSYSTEM=="block", RUN="/sbin/program" will execute the program only for block device events. ACTION="remove", SUBSYSTEM=="block", RUN"/sbin/program" will execute the program, if a block device is removed.