Which preposition to use with revocable

at Occurrences 2%

The office of lord-general was abolished; no intermediate rank between the lieutenant-general and the colonels was admitted; Fleetwood was named lieutenant-general, with the chief command in England and Scotland, but limited in its duration to a short period, revocable at pleasure, and deprived of several of those powers which had hitherto been annexed to it.

by Occurrences 2%

If any such immunity had been granted, it is still revocable by the legislature, and ought to be revoked, as contrary to the publick good, which is, in every charter, ultimately intended.

Which preposition to use with  revocable