She worked for Valdes-Fauli, Cobb & Petry in Miami, Florida, from 1980 until 1985, when she joined Holland & Hart as a senior associate.

[7] On July 27, 2000, President Bill Clinton nominated Arguello to the seat on the Tenth Circuit after John Carbone Porfilio assumed senior status.

Arguello's name was included as one of three that the two senators eventually jointly forwarded to the White House.

[2] On May 17, 2008, a television station in Denver reported that the White House had accepted Arguello as a Colorado district court nominee.

The Senate confirmed Arguello to her district court seat in a voice vote on September 26, 2008.

[7] On May 18, 2009, Arguello confirmed to a Denver television station that she had been approached by White House intermediaries one week earlier about being considered to fill a seat on the Supreme Court of the United States.

[15] She denied Sanderson's motion, writing that he and his attorney needed to serve all the defendants first before she would hand down a ruling.