Attorneys for Sun Editor-Publisher Brian Greenspun filed their request Thursday, arguing that a federally overseen joint operating agreement is at stake.
They say the time is now right for a temporary restraining order and a preliminary injunction against Stephens Media LLC.
U.S. District Judge James Mahan had ruled Sept. 6 that it would be premature to issue an order blocking talks about a sale.
Greenspun's attorneys point to a new letter Sept. 10 from Stephens Media offering to buy the Sun from Greenspun sibling trustees.
He argues that would end publication of the newspaper that's distributed as a daily insert in the Review-Journal.