Q: My father shot and killed a bald eagle when he was 14 years old. He is now 93, and he has the eagle displayed in his house. Is it illegal for us to keep it?

A: The bald eagle is protected by at least three federal laws: the Migratory Bird Treaty Act, the Bald and Golden Eagle Protection Act, and the Endangered Species Act. Together, these laws create sweeping mandates with respect to the collection of bald eagles.
A cursory review of each of these acts, taken in order, is necessary.
The Migratory Bird Treaty Act criminalizes the collection of hundreds of birds, including the bald eagle. Keeping a feather or an entire specimen can be considered trafficking. Thus, it is best simply not to keep whole or parts of regulated birds in one’s possession.
Perhaps most directly applicable, the Bald and Golden Eagle Protection Act prohibits the destroying or removing of nests of both Golden and Bald Eagles and bans the collection of their feathers.  Any kind of exception to this rule requires a permit specifically issued by the Secretary of the Interior.
Violation of the act can result in harsh criminal and civil penalties.
With respect to the criminal penalties, a mental intent requirement exists whereas mental intent is irrelevant in assessing a civil penalty. Thus, one who finds and keeps a feather without knowledge that it comes from a protected eagle may be able to avoid a criminal penalty but would still be subject to a potential civil penalty.
A memorandum attached to the Act indicates one of its purposes: to “facilitate the collection and distribution of scarce eagle bodies and parts” for use for Native American religious purposes. Thus, by banning possession by those not affiliated with a tribe, eagle feathers can be used more readily by Native American cultures.
In fact, the act requires appropriate federal agencies to collaborate in shipping eagles to the National Eagle Repository for distribution among Native Americans on a permit basis.
The act allows the possession of eagles for other purposes including by scientists and for museums.
Finally, the Act reads that “nothing herein shall be construed to prohibit possession or transportation of any bald eagle ... or any part, nest, or egg thereof, lawfully taken prior to June 8, 1940.”  Thus, the act ostensibly exempts your father’s eagle which was apparently collected before the act’s enactment. Problematic would be showing when the eagle was collected, unless you have taxidermy or other records indicating that date.
The Endangered Species Act makes it illegal to “harass, harm, pursue, hunt, shoot, wound, kill trap, capture or collect” endangered specifies without regard to whether the action is done maliciously. Again, although the specimen in your situation was killed years ago, it arguably could still likewise fall into this broad definition — especially in light of the fact that it would be difficult to show when it was collected.
All three of the acts have been subjected to various ranges of largely unsuccessful constitutional attacks. For instance, the Bald and Golden Eagle Protection Act has been targeted repeatedly, and withstood constitutional muster, along First Amendment grounds. Many have argued racial restrictions on persons that can apply for a permit should be removed.
Those possessing any portion of an eagle should take heed of the potential criminal nature of their actions. Thus, in answer to your question, although perhaps a beautiful family heirloom, the possession of the bald eagle possibly falls into the regulatory ambit of one or more of the above statutes.  
Although exceptions apparently exist, I would recommend having an attorney research these exceptions in more detail to guarantee your compliance with the myriad of federal laws applicable to the situation.
Apparently, the bald eagle, as our national symbol of freedom, is itself free of collection.