prerogative

The military fame of a subject was considered as an insolent invasion of the Imperial prerogative; and it became the duty, as well as interest, of every Roman general, to guard the frontiers intrusted to his care, without aspiring to conquests which might have proved no less fatal to himself than to the vanquished barbarians.

I hear my chair in the hall; and to keep Lord Marchmont waiting, when he has announced his intention of supping at home, far exceeds my prerogative; so good night, dearest, you will either see or hear from me to-morrow.