That didn't take long.

Just a few hours after newspaper chain Tribune Publishing announced that it inked an agreement to buy the Orange County Register and the Riverside Press-Enterprise for $56 million, the U.S. Department of Justice made good on its threat to file an antitrust lawsuit to stall the deal.

At the center of the government's lawsuit is the notion that, by owning four major newspapers in Southern California, Tribune Publishing would establish a monopoly in the region and have free reign to increase newsstand, advertising and subscription rates, according to The Associated Press.

The Department of Justice earlier this week sent a letter to a lawyer representing the OC Register warning that Tribune Publishing, which also owns the Los Angeles Times and the Riverside Press-Enterprise, would pose a "serious risk of harming newspaper readers and advertisers in Orange County and Riverside County."

But earlier today, newly minted Tribune Publishing CEO Justin Dearborn seemed confident that the bid would go through, releasing a statement that touted the company's purchase:

The successful bid for the business of Freedom Communications will allow the Orange County Register and the Press-Enterprise to continue providing a distinct local voice in their communities and deliver premium news and information to consumers across Southern California.

It remains to be seen how this development will affect the pending sale of the OC Register, but at the very least, it's likely to stall the transaction at least long enough for regulators to adjudicate their lawsuit. A Monday bankruptcy court hearing, described earlier today by Tribune Publishing as a formality to approve the deal, will likely present an opportunity for the Justice Department — or any other involved party — to air their grievances about the deal.