The Legal Information Institute (which is a great resource and also has the URL one would expect Cornell Law School to have) provides a table of popular names of acts. The (non-hyperlinked) example of a popular name the LII provides on its page about the United States Code is the “Wild Horse Annie Act.”
What is the Wild Horse Annie Act?
The LII’s table of popular names tells us that it was Pub. L. 86-234, Sept. 8, 1959, 73 Stat. 470, and is now codified at 18 U.S.C. § 47:
(a) Whoever uses an aircraft or a motor vehicle to hunt, for the purpose of capturing or killing, any wild unbranded horse, mare, colt, or burro running at large on any of the public land or ranges shall be fined under this title, or imprisoned not more than six months, or both.
(b) Whoever pollutes or causes the pollution of any watering hole on any of the public land or ranges for the purpose of trapping, killing, wounding, or maiming any of the animals referred to in subsection (a) of this section shall be fined under this title, or imprisoned not more than six months, or both.
(c) As used in subsection (a) of this section-
(1) The term “aircraft” means any contrivance used for flight in the air; and
(2) The term “motor vehicle” includes an automobile, automobile truck, automobile wagon, motorcycle, or any other self-propelled vehicle designed for running on land.
Annie herself was not a horse but a horse enthusiast.
The Rolling Stones’s take on wild horses is here.
The horse in Wild Hearts Can’t Be Broken is not wild, but apparently the hearts are (and possibly also the heads).