The Federal Communications Commission threw a penalty flag Thursday at Time Warner Cable, ordering the company to immediately put the NFL Network back on the Adelphia Communications and Comcast cable systems Time Warner got in its deal for much of bankrupt Adelphia’s system.

How long the channel will stay on the systems remains uncertain. The immediate penalty appears to be short-term, and even a big penalty is unlikely to keep the network on Time Warner’s system through the NFL season.

The FCC responded unusually swiftly to a complaint that NFL Enterprises filed earlier this week claiming customers of the affected systems got insufficient advance notice that the network was being discontinued when Time Warner Monday night closed its $12.5 billion deal for Adelphia. The NFL contends a 30-day notice is required.

Under the deal, Time Warner and Comcast each got chunks of Adelphia and then swapped some cable systems to give each company stronger market concentrations in particular areas.

While Comcast and Adelphia carried the NFL Network, Time Warner doesn’t, and, at least according to the NFL, talks with the NFL have been stymied by an argument about whether the network should be available to all viewers (the NFL’s desire) or on a sports tier for which consumers pay more (Time Warner’s position).

Because Time Warner has no contract with the NFL, it shut off the network to about 1 million homes when it took over the systems Tuesday morning. The NFL said the number of homes affected could top 3.7 million, but Time Warner said it picked up 3.3 million subscribers in the Adelphia deal and at most 1.3 million of them had the NFL Network.

The NFL said in its FCC complaint that it offered Time Warner a 30-day grace period to carry the network after the switchover but that the offer was rejected by Time Warner on July 27, the same day the company began running newspaper ads in some of the affected markets saying that the network would be dropped Aug. 1.

In today’s order the FCC didn’t take sides on the complaint, but ordered the NFL Network be put back in the lineups until it can resolve the complaint. It also ordered quick schedules for responses from both sides.

“We will act expeditiously,” FCC Chairman Kevin J. Martin promised.

In a statement, the NFL praised the FCC.

“We appreciate the FCC’s speedy action in response to our petition, and are gratified that the commission has acted to protect the interests of cable consumers-and NFL fans-throughout the country,” the NFL said. “We look forward to continuing discussions with Time Warner regarding long-term carriage of the NFL Network and are happy that in the interim our fans will have access to our ‘insider’ coverage of NFL training camps and the preseason as a result of this ruling.”

Time Warner Cable said it is reviewing the FCC’s order.

“This order was issued without offering us the opportunity to respond to the NFL Network’s allegations. We believe the FCC’s decision is wrong and we are considering our options,” the statement said.