[3] As a magistrate judge, he oversaw petty offense and misdemeanor cases on federal lands in the western part of the state.

[3] From 2002 until his appointment as a magistrate judge in 2012,[1] Gallagher was a contracted attorney with the Colorado's Office of the Alternate Defense Counsel, representing indigent defendants who could not be represented by the Office of the Colorado State Public Defender due to a conflict.

President Biden nominated Gallagher to the seat vacated by Judge William J. Martínez, who subsequently assumed senior status on February 10, 2023.

[3] Gallagher was unanimously rated "well qualified" for the judgeship by the American Bar Association's Standing Committee on the Federal Judiciary.

[10] On January 3, 2023, his nomination was returned to the President under Rule XXXI, Paragraph 6 of the United States Senate.