Be sure and read through the entire page at the link above.
Even though ARPA does not specifically mention "metal detecting", you need to understand what ARPA says about digging artifacts.
In addition to the above mentioned ARPA law, if you are detecting in Maryland, you must be aware of another law, the National Historic Preservation Act.
As confusing as the above laws may seem regarding metal detecting in Maryland, do not dig anything that you believe is an artifact, or anything that is older than 100 years.
Especially if you are on any State Lands.
If you want to detect on private property, then be sure you get written permission from the landowner.
For metal detecting Maryland town, village and city parks, you'll need to check with those local officials.
For Metal Detecting In Maryland State Parks, State Land and Beaches, here are some specific laws.
Relics, Treasures, and Metal Detectors
A. The policy of the Service is to safeguard the archeological resources under its care. The guidelines in B and C of this regulation shall be followed.
B. Without a permit from the Office of Archeology, Maryland Historical Trust, Department of Housing and Community Development, and the Department, an individual may not dig in search of buried relics or treasures, remove prehistoric or historic artifacts, or use metal detectors, except as provided in §D of this regulation, within the boundaries of lands, beaches, or under waters controlled by the Service.
C. Permits are issued to archeologists and other qualified individuals who present a plan for scientific investigation to be carried out under provisions of the Maryland Archeological Historic Properties Act, Article 83B, 5-623-----5-628, Annotated Code of Maryland. Copies of the law and application for permit can be obtained from the Chief, Office of Archeology, Maryland Historical Trust, 100 Community Place, Crownsville, MD 21032.
D. Metal Detector Exception.
(1) An exception to the permit requirements of this regulation is for the use of a metal detector in the search for modern coins, jewelry, and other items on designated swimming beaches operated by the Service, with the exceptions of Point Lookout and Calvert Cliffs.
(2) An individual shall obtain permission to use a metal detector as set forth in this regulation from the Service.
(3) A metal detector may be used during normal park hours with the following exceptions: (a) 9 a.m. through dusk from May 30 through Labor Day; and (b) Other times at the discretion of the park manager..
I cannot be responsible for any outdated laws regarding metal detecting in Maryland from the time of this posting.
This page is a synopsis of the ARPA law
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