Maryland Statutes
Subtitle 3 - Process
Section 6-305 - When Witness or Party May Not Be Served

(a)    A nonresident person who is within the State for the purpose of testifying in or prosecuting or defending an action may not be served with process.
    (b)    A nonresident person passing through this State to or from another state in response to a summons to testify may not be served with process. This subsection does not apply to process arising from acts done by the person after his entry into this State.