While there, he earned the faculty's William and Ellen Cooney Hoye Award and was a junior staff member of the Drake Law Review.

While attending Drake University Law School, he conducted legal research for Iowa Supreme Court Chief Justice Mark Cady.

[4][5] Gregg was appointed by Governor Terry Branstad to serve as the Iowa State Public Defender on December 8, 2014.

[8][9] Due to ambiguities in Iowa's constitution and a controversial advisory opinion issued by Attorney General Tom Miller, there was some dispute regarding Reynolds' power to appoint a new lieutenant governor who would ascend as her successor if she left office prior to the expiration of Branstad's sixth non-consecutive term.

[13][14] Gregg resigned on September 3, 2024, effective immediately, to become president and chief executive officer of the Iowa Bankers Association.