[3] At St. Thomas, he founded the nation's first law school clinic on federal commutations,[4] and he has advocated for an expansive use of the presidential pardon power.

The character of "Professor Joe Fisher" in the film American Violet is based on Osler's work with the ACLU and former student David Moore in confronting unjust crack prosecutions in the city of Hearne, Texas.

[42] An article Osler co-authored with Rachel Barkow for the University of Chicago Law Review was highlighted in a lead editorial in The New York Times, in which the Times' editorial board expressly embraced Barkow and Osler's argument for clemency reform.

"[52] He is a founding member of Law Enforcement Leaders to Reduce Crime and Incarceration, a national group of former and current prosecutors and police chiefs.

[53] Osler was also the lawyer for Weldon Angelos, who was freed in 2016 after serving 12 years of a 55-year sentence on a marijuana and gun possession conviction.

[57] In August of 2023, Osler began a leave of absence from St. Thomas to serve as Deputy Hennepin County Attorney and Director of the Criminal Division under Mary Moriarty.

In August of 2024, Osler promoted Minnesota Governor Tim Walz as a potential running mate for presumptive Democratic presidential candidate Kamala Harris.