Which preposition to use with emptive

at Occurrences 1%

I’ll sing to you a fine new song, made by my blessed mate, Of a fine Australian squatter who had a fine estate, Who swore by right pre-emptive at a sanguinary rate That by his rams, his ewes, his lambs, Australia was made great Like a fine Australian squatter, one of the olden time.

Which preposition to use with  emptive