Well... I spoke too soon... It looks like a local jurisdiction in Maryland can regulate the operation of bicycles. Here's an excerpt from § 25-102...
§ 25-102.
(a) The provisions of the Maryland Vehicle Law do not prevent a local authority, in the reasonable exercise of its police power, from exercising the following powers as to highways under its jurisdiction:
(8) Regulating the operation of bicycles, requiring them to be registered, and imposing a registration fee;
Great.