Prior to his appointment, he was a professor at the Antonin Scalia Law School of George Mason University and an official in the first Trump administration.

Menashi's grandparents were Jewish immigrants from Iraq and Ukraine; his maternal grandfather's relatives were murdered in the Holocaust.

[5] Menashi served as a law clerk to Judge Douglas H. Ginsburg of the U.S. Court of Appeals for the District of Columbia Circuit from 2008 to 2009.

While at Kirkland & Ellis, Menashi was a Research Fellow at the New York University School of Law and the Opperman Institute for Judicial Administration for three years, from 2013 to 2016.

[17] During his hearing, Menashi was criticized by senators from both parties for refusing to answer their questions regarding the legal advice he gave on the Trump administration's immigration policies.

2021), Menashi ruled that a prohibition on firearms ownership based on an ex parte order of protection violates the Second Amendment.

[27][28] Menashi wrote that the prosecution, which had been initiated by a judge, violated the separation of powers put forth by the United States Constitution.

2024), Menashi dissented from the Second Circuit's denial of en banc review in a decision in which it had concluded that it did not have personal jurisdiction over the Palestine Liberation Organization or the Palestinian Authority in suits concerning deaths and injuries to United States citizens from terrorist attacks overseas.

2024), Menashi dissented to argue that the town of Southold, New York had violated the takings clause of the Fifth Amendment by using eminent domain to stop the property owners from building a hardware store on the land.

2024), Menashi wrote an opinion reinstating bribery and fraud charges against former Lieutenant Governor of New York Brian Benjamin.