Hawkeye, Captain America and Black Widow are too much for the Pentagon to handle. The Transformers are cool, though. (Walt Disney Pictures)

Warning: This post might contain spoilers for the six people who haven’t yet seen The Avengers.

The Pentagon doesn’t mind lending an assist to big-budget Hollywood blockbusters about Martian invasions or giant robots from outer space, but the U.S. military apparently draws the line at epics about a team of (mostly) Earth-born superheros.

Wired.com’s Spencer Ackerman reports that the Defense Department backed away from lending its assistance to the producers of Marvel’s The Avengers, which made its North American debut last weekend with a box-office haul of about a gazillion dollars.

Although the Pentagon often helps big summer blockbusters that feature military settings, it declined to participate in The Avengers for what it saw as a lack of realism in its “its treatment of military bureaucracy,” Ackerman reports. Apparently, S.H.I.E.L.D., the global peacekeeping apparatus to which Iron Man, Captain America, Thor and the Incredible Hulk answer, was just too irregular for the brass:

“We couldn’t reconcile the unreality of this international organization and our place in it,” Phil Strub, the Defense Department’s Hollywood liaison, tells Danger Room. “To whom did S.H.I.E.L.D. answer? Did we work for S.H.I.E.L.D.? We hit that roadblock and decided we couldn’t do anything” with the film.

So it was a matter of taking orders, and not, say, the depiction of a flight-capable aircraft carrier that turned the military away from helping Marvel Studios achieve its biggest movie to date?

But the military has been involved with plenty of explosion-filled tentpoles before, and has several more projects in the pipeline. Perhaps the most visible partnership between Hollywood and the Pentagon has been Michael Bay’s Transformers series, in which each installment has featured military equipment and officers as willing co-stars. Steven Spielberg’s 2005 rendition of War of the Worlds included several scenes in which real-life army units made uphill charges against the invading Martian tripods.

Then again, maybe it is a chain-of-command thing: Optimus Prime is depicted as more subservient to the Pentagon than, Tony Stark is to S.H.I.E.L.D. and its director, Gen. Nick Fury. (Who isn’t always the most obedient himself.)

As Ackerman writes, that’s enough to give the Pentagon pause:

But the ambiguity around what exactly S.H.I.E.L.D. is provides a vexing complication. If it’s an American governmental agency, what kind of constitutional authority does it exercise over the military? If it’s an international body, as the movie text suggests and Strub determined, are U.S. military personnel and equipment on loan to it through some kind of United Nations Security Council resolution? The questions may seem picayune, but they’re precisely the stuff that can cause an image-conscious military to yank its cooperation from a movie.

Not that Marvel hasn’t previously met the military’s approval. The Defense Department lent the makers of 2008’s Iron Man a pair of F-22 Raptors. It’s the most action the model has ever seen—the notoriously faulty planes have never actually been used in combat situations. And while the Pentagon wound up squeamish about The Avengers, it wasn’t before military officials permitted director Joss Whedon to film Humvees rolling around battle-strewn Manhattan.