TV-over-the-Internet startup Aereo has one last legal argument it's going to use to try to keep itself alive, but it failed to gain any traction at the US Copyright Office.

The Supreme Court ruled against Aereo last month, saying the company can't keep using arrays of tiny antennas to justify its streaming of TV broadcasts over the Internet. In a 6-3 opinion, the high court found that Aereo looks too much like a cable company to re-broadcast for free.

In a last-ditch effort, Aereo has tried to embrace the ruling, offering to pay the state-set retransmission fees that cable companies must pay to copyright holders. The retransmission fees are low, around one percent of revenue for a cable company.

Whether that argument will work in court is yet to be seen (although it already failed once before, with a company called ivi TV.) But Aereo's argument isn't working at the US Copyright Office.

"In the view of the Copyright Office, Internet retransmissions of broadcast television fall outside the scope of the Section 111 license," the office wrote in a letter dated July 16. The letter was first obtained CNBC, which reported its contents earlier this morning. The letter was later acquired and published (PDF) by the National Association of Broadcasters, a trade association opposed to Aereo.

In the letter, the office said it won't reject Aereo's filings but will rather "accept them provisionally" since its case is still in court, according to CNBC. Aereo didn't immediately comment on the letter.

It's no surprise that the US Copyright Office, which tends to see things along the same lines as the content industry, would choose not to side with Aereo. Without a ruling from a federal judge that it can pay the retransmission fees, Aereo's new plan is going nowhere. And broadcasters will no doubt fight Aereo tooth and nail, as they did against ivi TV.

"The Copyright Office's position was already the policy at the time of ivi TV," noted Michael Risch, a law professor at Villanova University, in an e-mail exchange with Ars. "In addition, the court that ruled against ivi did so in part by giving deference to the Copyright Office's interpretation, that the statute excludes internet transmissions. Aereo will have to overcome that deference in its case."

Even for cable companies that do pay retransmission fees, TV companies have argued that their content still can't be moved around digitally without their permission because of their "public performance" rights. That's why they're fighting "TV Anywhere" schemes like the Dish Hopper.