Admin input isn't needed. There is nothing in the licensing agreement that says you cannot backup the software. Therefore, if we are not for to "agree" not to, then the law that prevails is the default copyright law. It is well established in black letter and case law that absent any licensing agreement where you "sign" away your rights, fair use includes the right to back up your software.
The admins can say it's legal, the admins can say it's not legal. They can talk as much as they like, but until and unless the text of any licensing agreements they put up includes a clause specifically forbidding users to back up the software they obtain here, then it's perfectly legit.
My guess is that they would prefer to practice strategic ambiguity about the issue. I don't believe they think they can get away with actually forbidding backups. If they leave the issue ambiguous, then the very murkiness of the water acts as a check against people reinstalling. Ambiguity serves their purposes.