As it turns out, The DOJ isn't ready to let a federal judge's decision to kill its challenge to the AT&T-Time Warner merger go unchallenged.

As a reminder, Judge Leon advised the government not to seek a stay of the ruling to prevent the DOJ from pushing the deal past its deadline, which was at that time only days away.

"The Government has failed to meet its burden of proof to show that the merger is likely to result in a substantial lessening of competition," he wrote in his ruling. Furthermore, Leon declared that seeking a stay would be a "manifest injustice."

A month after the judge's ruling was handed down - and after the judge effectively warned the federal government not to appeal - the DOJ has done just that, reviving the federal government's fight to block the $85 billion 'vertical integration' deal, the Wall Street Journal reported.

As CNN reports, the case will now go to the D.C. Circuit Court of Appeals, where a three-judge panel will hear the appeal.

In theory, the case could end up in front of the Supreme Court, something some people in the legal community have been hoping for, since the Supreme Court has not taken up a merger case since the 1970s.

David McAtee, AT&T's General Counsel exclaimed:

"The Court's decision could hardly have been more thorough, fact-based, and well-reasoned. While the losing party in litigation always has the right to appeal if it wishes, we are surprised that the DOJ has chosen to do so under these circumstances. We are ready to defend the Court's decision at the D.C. Circuit Court of Appeals."

The news sent shares of AT&T lower just under 2% in the after-market:

This is a 3-week low for AT&T

Investors will now be looking out for more information regarding what aspect of the judge's ruling the DOJ will choose to challenge.