Source: Office of the Secretary of State (Maryland)
http://www.dsd.state.md.us/comar/Sub...rch=29.04.08.*

Direct link to law:
http://www.dsd.state.md.us/comar/com...9.04.08.13.htm

QUOTE:

29.04.08.13

.13 Armed Private Detectives; Documentation of Weapon Information Required.

A. If a private detective agency employs armed private detectives, the agency shall maintain a list for each armed private detective of:

  1. The weapon type;
  2. The weapon's serial number; and
  3. Whether the weapon is agency owned or personally owned.

B. The personnel file for each armed employee shall contain a photocopy of the handgun permit for each private detective who is armed.

C. An armed private detective may only use a weapon for which the private detective has been qualified to shoot and for which the private detective has submitted documentation identifying the weapon and the qualifying score to the Licensing Division Handgun Permit Section before carrying that weapon, in accordance with Public Safety Article, Title 5, Annotated Code of Maryland.

D. Private detectives may not be armed unless they possess a valid handgun permit.