[2] The act covered the management, protection and study of "unbranded and unclaimed horses and burros on public lands in the United States."

Although the BLM struggled to implement adequate herd management in many areas, in 1973 they began a successful program for rounding up excess numbers, and adopting out these captured horses and burros to private owners.

Administrative challenges to BLM's management and implementation of the act have been made to the Department of the Interior's Board of Land Appeals.

Objections have been varied, focusing on constitutionality, and legal status of the animals, but the Act has been upheld in all instances, including Kleppe v. New Mexico, before the United States Supreme Court.

Beginning with its enactment, it required studies of the habits and habitats of free-ranging horses and burros, permitting public land to be set aside for their use.

[4][5] In addition, the act required that these horses and burros be protected as "living symbols of the historic and pioneer spirit of the West.

"[6] The BLM was tasked with identification of the areas where free-roaming horses and burros were found; there was no specific amount of acreage set aside,[7] and the Act required management plans to "maintain a thriving natural ecological balance among wild horse populations, wildlife, livestock, and vegetation and to protect the range from the deterioration associated with overpopulation.

The BLM was also permitted to close public land to livestock grazing to protect wild horse and burro habitat.

[16] The United States Forest Service periodically gave ranchers notice to round up their strays and thereafter shot any remaining horses.

On September 8, 1959, President Dwight D. Eisenhower signed into law the Hunting Wild Horses and Burros on Public Lands Act, Pub.

[26] In Nevada, state law permitted ranchers to round up any unbranded horses on their private land and slaughter or sell them.

[27] Concerned about these practices, and about continuing horse hunts in unprotected areas, International Society for the Protection of Mustangs and Burros of which Johnston was the first president, began working to pass federal legislation to protect feral horses throughout the U.S.[26] She was joined by a number of prominent people, including country music singer Judy Lynn, Gunsmoke actress Amanda Blake, and Manchester Union Leader publisher and conservative William Loeb III,[27] who continued to lobby for federal rather than state control over the disposition of free-roaming horses.

Ranchers were given a specified time period following passage of the Act to claim their horses, and any remaining unbranded and unclaimed herds roaming BLM or Forest Service became the property of the federal government.

[38] The Act left range management policy unresolved in many respects, although it did specify that BLM and the Forest Service consult with state wildlife agencies.

[40] In November 1971, the BLM announced a major effort to save the Pryor Mountain herd from starvation after a poor summer growing season left vegetation on the range stunted.

[37] Pursuant to the 1978 amendments to the Public Rangelands Improvement Act (PRIA),[42] the BLM established 209 herd management areas (HMAs) where feral horses were permitted to live on federal land.

[44] The program took advantage of provisions in the Act to allow private "qualified" individuals to "adopt" as many horses as they wanted if they could show that they could provide adequate care for the animals.

[46] In 1978, Public Rangelands Improvement Act (PRIA)[44] authorized the BLM to relinquish title to adopted horses after one year of satisfactory private maintenance.

Through 2001, the Adopt-a-Horse program was the primary method of disposal of excess feral horses from BLM and Forest Service land.

[47] As of 2013, the BLM is also researching the possibility of spaying some mares to permanently prevent pregnancies,[48] and a new vaccine, the "first single-shot, multiyear wildlife contraceptive for use in mammals", has been approved for use by the Environmental Protection Agency.

Up until then, feral horses and burros were considered to be under the jurisdiction of State estray laws, and managed as unclaimed livestock that the Federal government[25] had no right to interfere with.

[51] To test this assertion, in 1974 the New Mexico Livestock Board seized 19 free-roaming feral burros which were preventing cattle from using a watering hole on federal land.

The District Court, however issued a summary judgement for the government against the contention that feral horses who ate grass or drank water on privately owned lands had "taken" these resources from the ranchers in violation of the "takings clause" of the Fifth Amendment to the U.S. Constitution and the government must compensate the private landowners $500,000.

[59] In March 1987, the Animal Protection Institute sued the Department of the Interior, arguing that BLM was turning a blind eye to "adopters" who obtained horses with the intent to slaughter.

In 2011, a case was brought before the U.S. District Court in Nevada, regarding a roundup in that state, alleging in part that helicopter pilots flew too close to horses.

The judge in that case issued a temporary restraining order against the "mistreatment of mustangs during BLM gathers", including inadequate distance between helicopters and animals.

"[68] Burns was reportedly acting on behalf of ranching interests, who wished more of the horses removed from federal land.

[71] BLM suspended the sales program in April 2005 and resumed it in May 2005 after implementing new requirements to deter buyers from slaughtering the animals.

[72] In January 2007, the United States Court of Appeals for the Fifth Circuit ruled that a 1949 Texas law banned the possession, transfer, or sale of horse meat.

[73] In 2008, the Government Accountability Office (GAO) concluded BLM was not in compliance with the 2004 amendment, as the department had imposed limitations on the sale of excess horses to help ensure that they were not slaughtered.