The government doesn't have any antitrust issues with the Cox/Fox stations swap.
That is according to a list of deals given early termination of their Hart-Scott-Rodino antitrust reviews because the Justice Department and Federal Trade Commission, which divvy up such reviews, have no issues that require conditioning or seeking to block the deal.
The FCC has yet to announce its decision on the deal, but usually coordinates with Justice/FTC so its decision is also anticipated in relatively short order.
The government decision was relatively swift given that Cox and Fox only announced June 24 that they had struck a deal, subject to government approval, to trade Fox's WHBQ Memphis and WFXT Boston for Cox's KTVU and KICU, both San Francisco.
The deal does not require any waivers of FCC ownership rules, one reason FCC approval is likely.