Copyright laws apply to the entertainment industry as well as to manufactured products. Entertainment laws can be quite complex. The more popular an entertainer, author, or artist's works or production become, the more people want a piece of them. Copyright contracts must be carefully drafted to ensure that the performer or creator's rights are fully protected. A minor mistake could open up a loophole for someone to infringe upon those rights.
When Joseph Shuster, a co-creator of Superman sold his rights to DC Comics back in 1938, he probably had no idea the "man of steel" would become, and remain, so popular again in the late 20th and early 21st century. Superman's popularity and increased value is no doubt the reason Shuster's siblings signed a 1992 agreement with DC, which granted them lifetime pensions. According to a Los Angeles district judge, this contract canceled out the 1938 contract.
However, Joseph Shuster's heir filed for a termination of the 1938 contract in 2003 to attempt to reclaim the rights that had been sold to DC Comics, whose parent company is Warner Brothers. The federal appeals panel revoked the 1938 assignment and re-granted the copyrights of Superman to DC comics per a majority ruling of 2-1. One judge argued against the ruling, stating that there was not enough evidence to show that Shuster's siblings had authority to supersede the original copyright agreement in 1938 to start with.
Also in 1992, the copyright law only allowed a surviving spouse or child to exercise the right of termination. In 1998, Congress changed that law to include others, such as executors for authors, representatives and trustees. So according to this dispute, the siblings would not have had the right to override the original agreement.
The copyright to Superman is of much more value now than it was in 1938. It is impossible to know what the original author's wishes would be since he apparently is no longer around. This is why it is so important to ensure that contracts are thorough, dotting all the i's and crossing all the t's. Laws also change over periods of time making it even more difficult to predict what kind of dissent could come up in the future.
Source: courthousenews.com, "GoldieBlox Pulls Beastie Boys Song Superman Artist's Heirs Lose Copyright Claims" Tim Hull, Nov. 22, 2013