De Soto National Memorial was formed by Act of Congress in 1948. Here is the legislation:
For the purpose of establishing an appropriate memorial to Hernando DeSoto, the Secretary of the Interior is authorized, in his discretion, to acquire on behalf of the United States, by donation, by purchase with donated funds when purchaseable  at prices deemed by him reasonable, or by condemnation with donated funds, such lands and interests in land within an area of not to exceed thirty acres as he may select in the vicinity of Tampa Bay and Bradenton, Florida, and to construct thereon a suitable memorial structure, together with such connecting roads and public facilities as may be desirable.
 So in original. Probably should be “purchasable.”
The Superintendent has the authority to create such rules as support the safe and effective operation of De Soto National Memorial. Click here to view the Compendium of these rules.
CODE OF FEDERAL REGULATIONS
TITLE 36, CHAPTER 1
Compendium of Designations, Closures, Request Requirements and Other Restriction imposed under the discretionary authority of the Superintendent.
In accordance with regulations and the delegated authority provided in Title 36, Code of Federal Regulations, Chapter 1, Parts 1 through 7, authorized by Titles 16, United States Code, sections 3, the following regulatory provisions are established for the proper management, protection, government and public use of the portions of De Soto National Memorial under the jurisdiction of the National Park Service.
Unless otherwise stated, these regulatory provisions apply in addition to the requirements contained in 36 CFR, Chapter 1.
Section 1.5 Closures and Public Use Limits
(a)(1) De Soto National Memorial will remain open for public use from sunrise to sunset except as noted below:
The park Visitor Center/Museum will remain open from 9:00 am to 5:00 pm seven days a week.
The park road and parking area will remain open to motor vehicles from 9:00 am to 5:00 pm.
(a)(1) The area west of the park adjacent to the public entrance, which is used for general maintenance is closed to the general public. This is a work area containing heavy equipment, power tools and chemicals.
(a)(1) During emergency situations the park may be closed for short periods of time without advance public notice.
(a)(1) The park Visitor Center/Museum will be closed New Years Day, Thanksgiving and Christmas Day.
Section 1.6 Permits
(c) In accordance with 36 CFR 1.7, the following activities require special permits:
Collection of research specimens
Sale/distribution of printed materials
Display of commercial notices or ads
Commercial photography and filming
Construction on Federal property
Scattering of human ashes from cremation
Activities involving first amendment rights will take place at the northeast corner of the parking area, along the sidewalk and grass shoulder.
Special events may take place only along park roadways or in the lawn areas adjacent to Visitor Center.
Section 2.1 Preservation of Natural, Cultural and Archeological Resources
(a)(1)(ii) Climbing of trees is prohibited. All trees are part of the cultural landscape and as such need protection from harm. Climbing of trees is a safety hazard.
(a)(4) The taking of driftwood is prohibited. Driftwood adds to the stabilization of the beach.
(c)(1) A reasonable quantity (maximum on gallon per family/group per day) of seagrapes may be gathered from within the boundaries of the park for personal use. The gathering of seagrapes is a traditional activity at the park. Current limitations show no adverse impact to the survival of the plant.
(c)(1) The taking of the fruit of the Prickly Pear Cactus is prohibited. Removal of the fruit inhibits plant growth and exposes the thorns. The shell midden Prickley Pear is a protected (Threatened and Endangered) species.
Unoccupied sea shells may be gathered by hand on shorelines, except where such shells are found in an archeological site (ARPA, 1979).
Section 2.10 Camping
(a)(9) Camping of any kind tent, R.V., or other is prohibited on park property.
Section 2.11 Picnicking
The consumption of food or beverages in the Visitor Center auditorium is prohibited.
Section 2.13 Fires
(a)(2) The use of stoves, grills, charcoal, or other open fire is prohibited.
Section 2.14 Sanitation and Refuse
(a)(3) Cleaning or washing seashells in public restrooms or drinking fountains is prohibited. Sand from shells clogs the drain system.
Section 2.15 Pets
(a)(5) All visitors shall be responsible for disposing of their pets excrement. Excrement is a health hazard and unsightly. Excrement must be disposed of by placing it in a paper/plastic bag and putting it in a refuse receptacle or by taking it home with them.
(a) Pets running at large are considered a hazard to the public and will be controlled and after a reasonable time and following reasonable attempts to notify the owner, will be turned over to Manatee County Animal Control.
Section 2.16 Horses and Pack Animals
Horses and pack animals are prohibited in the park. The trails are too narrow and congested for this activity.
Section 2.20 Skating, Skateboards, and Similar Devices
Using roller skates, in-line skates, skateboards, roller skis, coasting vehicles or similar devices is permitted on paved roadways and on sidewalks between the hours of sunrise and 8:00 am and 5:00 pm to sunset provided such use does not create a public hazard, or damage, deface or destroy Federal property.
Section 2.21 Smoking
(a) Smoking is prohibited in all Federal building (Executive Order 13058, Federal Register August 13, 1997)
Section 2.22 Property
(b)(2) Unattended motor vehicles located in the visitor parking area after the designated closing time may be towed away at the owner of record’s expense.
Section 2.23 Recreation Fees
(a) Fees for specified recreation activities and weddings have been established.
Section 2.35 Alcoholic Beverages and Controlled Substances
(a)(3)(1) The following areas are closed to the consumption of alcoholic beverages:
The park Visitor Center/Museum building.
The visitor parking area and Living History Camp.
The park trails.
Section 2.52 Sale or Distribution of Printed Matter
The sale and distribution of printed matter shall be limited to the park public parking area. Other areas of the park are used for walking, fishing, and solitude.
Section 4.3 Bicycles
(c) Bicycles are prohibited on park trails. Trails are narrow and can be crowded. Bicycles are a hazard to pedestrians.
Section 4.17 Speed Limits
(b) The maximum speed limits on all public roads in the park are posted.