Hollywood studios, however, are loath to slap their superhero offerings with an R rating. The one film daring to break the rule was Fox's Deadpool, which stunned in earning north of $772 million at the worldwide box office earlier this year despite the restrictive rating.

Deadpool has prompted plenty of debate about whether other studios should follow suit; so far, no one else has been willing to make that move.

Generally speaking, there can be a fair amount of violence in a PG-13 title, but language and sex are another matter.

Suicide Squad, which revolves around an irreverent band of supervillains, is rated PG-13 for sequences of violence and action throughout, disturbing behavior, suggestive content and language, according to the ratings board.

Set to open in theaters Aug. 5, Suicide Squad stars Will Smith, Jared Leto, Margot Robbie, Joel Kinnaman, Viola Davis, Jai Courtney, Jay Hernandez, Adwale Akinnuoye-Agbaje, Ike Barinholtz, Scott Eastwood and Cara Delevingne.