[10][11] His father had originally come to the United States legally in 1943 as part of the bracero program, and ultimately received a green card.

[9][7] In order to commute from his house to the high school, he needed to take three different Chicago Transit Authority busses.

[12] Ruiz began his college career attending University of Illinois at Urbana-Champaign in its engineering program.

[7] However, by February of his freshman year, he was failing several classes, which he would retrospectively attribute to, "a combination of being unfocused and enjoying campus life too much.

"[7] He dropped-out of the school, returning home and enrolled himself at Thornton Community College, while working part time as an auxiliary clerk at the American Medical Association.

[4][10] While at University of Chicago Law School, he attended classes taught by then-professors Barack Obama and Elena Kagan.

[4][8][10] While attending Thornton Community College, Ruiz worked as an auxiliary clerk at the American Medical Association.

[4] Since September 2021, Ruiz has served as chief operating officer and general counsel to the Vistria Group.

[10][16] Ruiz was on the American Bar Association's Commission on Hispanic Legal Rights and Responsibility, to which the president of the ABA had appointed him in August 2013.

[22] Amid the COVID-19 pandemic, Ruiz announced that the Chicago Bar Association would be waiving the administrative fee that it normally charged callers on its hotline who later engaged the attorney they spoke with for a consultation.

[10][16] Politically, Ruiz supported the campaigns for office of his former law school professor Barack Obama.

[3][10] In September 2004, Ruiz was appointed by Governor Rod Blagojevich as chairman of the Illinois State Board of Education, becoming the first Hispanic individual to hold the position.

[26][29] During his tenure, Ruiz reacted to a school district violating federal law by refusing to enroll an undocumented immigrant student by taking the lead in having the Illinois State Board of Education, in an unprecedented move, cut the state funding of the school district in question.

[34] Immediately after becoming interim CEO, Ruiz suspended $20 million no-bid contract that had been granted to SUPES Academy at the urging Byrd-Bennet, who previous worked for the company, in 2013.

[41] His former seat on the board remained vacant until mayor Lori Lightfoot appointed Jose M. Muñoz to it in September 2019.

[42] Ruiz unsuccessfully ran for the Democratic Party nomination 2018 Illinois Attorney General election, placing sixth in a crowded field of eight candidates, receiving 5.4% of the vote.

The campaign's finance co-chairs included former United States secretary of commerce Penny Pritzker, Chicago Cubs co-owner and Lambda Legal board member Laura Ricketts, and former Exelon CEO John Rowe.

[11] Among Ruiz's campaign promises were to protect the state's residents from what he considered to be attacks on them by then-President Trump, to implement criminal justice system reform, to strengthen the police, and to work to "remove weapons from the streets".

[11] In reaction to the Cook County Democratic Party's decision to endorse Kwame Raoul for the office, Ruiz criticized what he characterized as the county party organization's decision to, "slate a fellow political insider", as being, "disappointing – but sadly, not surprising.

B. Pritzker designated Ruiz, alongside Daniel Hynes and Christian Mitchell, to be one of three deputy governors.

[52] Ruiz told the Chicago Sun-Times that he, "wasn’t looking to leave, but a great opportunity to return to private practice presented itself.

"[53] Governor Pritzker credited Ruiz, upon his departure with having made, "an enormous difference for our entire state’s education systems.

"[53] In October 2023, Governor Pritzker nominated Ruiz to serve on the University of Illinois Board of Trustees for a term lasting through 2029.