I suggest you do the same. The Maryland legislature was not placed under house arrest in September 1861. Only 11 were detained, and since they were planning on trying the take Maryland into the rebellion then going on what exactly did you expect to happen? Maryland was not an "occupied Southern state" since the legislature had voted not to secede on April 29, 1861.
April 19, 1861, the soldiers of the 6th Massachusetts Volunteers, moving through Baltimore on the way to Washington, were attacked by a pro-Southern mob (not 'rabble,' but including businessmen and 'respectable people'.
Rather than consider this an anomaly, consider the lines from the State Song:
"Avenge the patriotic gore/That flecked the streets of Baltimore."
Maryland had already been invaded.
"Meanwhile, on April 27 (1861) Lincoln authorized the suspension of habeas corpus. This meant that the military authorities could make summary arrests of persons thought to aiding the Confederacy or attempting to overthrow the government. Such persons could be detained indefinitely without judicial hearing and without indictment, and the arresting officer was not obliged to release them when a judge issued a writ of habeas corpus."
By the vote of April 29, Maryland had a gun to its head.
It was occupied by Union troops and Northern State Militias, Habeas Corpus had been suspended, and any who voted to seceede could be "detained" indefinitely without charges or trial or bond.