Md. Code, Transportation § 21–103

(a) (1) A person may not willfully disobey any lawful order or direction of any police officer.

(2) This subsection may not be construed to authorize a police officer at a motor vehicle checkpoint, as defined in § 25–114 of this article, to target only motorcycles for inspection or evaluation, except as appropriate at a police checkpoint established as part of a police search or investigation.

(b) (1) A police officer may summon witnesses to testify under oath on any charge brought under the Maryland Vehicle Law.

(2) A person may not willfully disobey a summons.