However, Fawcett decided to fight Detective's allegations that Captain Marvel, the star character of their Whiz Comics periodical, was also an illegal copy of Superman.

[2] When the action went unheeded, Detective and Superman, Inc. filed suit against Fawcett in September 1941,[2][3] naming Republic as a co-defendant.

[3] National's argument was that Captain Marvel's main powers and characteristics (super-strength, super-speed, invulnerability, a skin-tight costume with a cape, and a news reporter alter ego) were derived directly from those of Superman.

[5] Fawcett countered in two ways: by providing examples of Captain Marvel performing those feats at even earlier points of publication, or by providing examples of other heroic comics characters such as Popeye or Tarzan performing those feats in earlier published comic strips.

Judge Hand's ruling in National's favor reversed a part of the trial court's decision.

The case was sent back to a lower court to determine whether specific elements, such as storylines and superpowered feats, constituted infringement.

[4] Superhero comics sales had decreased dramatically during the early 1950s, and Fawcett decided that it was not worthwhile to continue fighting National.

This character enjoyed similar popularity in the 1950s and was revived in the 1980s, and itself became the subject of a copyright and trademark dispute after the publisher of its North American reprints ceased operations.

Captain Marvel remained out of print for the rest of the 1950s and the entirety of the 1960s, a period during which superhero comics regained their popularity.

[8] National v. Fawcett is still an often-referenced case in the areas of copyright law and plagiarism because of its readily-accessible subject matter, and the popularity of its author, Judge Hand, among legal scholars.