[2][3][4] Prior to becoming president,[5] Greiner served in other capacities in the University at Buffalo Law School, and in UB's administration.

[6][17] Greiner began his career at UB in 1967 as a member of the University at Buffalo Law School,[7][11][15][17][18] serving as Chair of the Legal Studies Department.

[2][7][28] By locating a previously unused state law saying that alumni associations can utilize private monies for dormitories, Greiner's research led to the construction of five apartment-style buildings for 2,100 UB students.

[31] In 1993 and during Greiner's tenure, the two universities expanded their agreement to include additional joint programs for students, faculty, and staff.

[32] In November 2002, Greiner led a delegation to Turkey, and signed an agreement with Istanbul Technical University for student and faculty exchanges.

[33] Greiner further developed international education ties with Cuba in 1999 regarding UB's program in Havana with Fernando Remirez de Estenoz, Cuban envoy to the United States.

[36] Greiner was supposedly unaware of these actions, placing responsibility for them on UB's athletic director, Nelson Townshend.

[36] So, annual recruitment visits were decreased, overall, from 12 to 8, a reduction that UB's administration believed to be unnecessarily harsh and planned to appeal.

[36] In 1996, UB held a university-wide referendum that was open to students regarding two issues on Greiner's agenda, including privatization and differential tuition.

[37] In October 1998, Cuthbert Ormond Simpkins, a surgeon and UB professor in the School of Medicine and Biomedical Sciences of four years, was denied tenure by Greiner.

[39] Simpkins received a letter dated October 1998 from UB Provost Thomas Headrick thanking him for his service, including a statement from Greiner that denied him continued support for a tenure track position.

[40] After Greiner secured the move to Division I-A in 1999, the UB football team lost 21 of 23 games in its first two seasons.

[41] UB's record from 1999 to 2003 was 6-39 (.153) since joining the I-A level, and 3-29 (.103) versus MAC division opponents during that time period.

[43] Greiner stated that reasons for building UB's athletic program included the attraction of out-of-state students, and alumni.

Student enrollment had declined, full-time faculty positions had decreased by 100 people, and funding was being more specifically directed to certain programs, such as athletics and information technology, rather than others.

[44] While college entrance Scholastic Aptitude Test (SAT) scores had increased, UB's status as a highly ranked research university in the United States had decreased since 1989 under the leadership of Steven Sample.

[46] Greiner rebutted Shechner's concerns regarding UB's reductions in student enrollment, the number of full-time faculty, decreased monies directed toward academics, and others.

[46] Among issues addressed by Greiner were the expanded use of student activity fees, UB's partnerships in the community, the state's capital investment program of nearly $200 million, more than $50 million used for student housing, and that UB adds $1.6 billion to the local economy in the Buffalo area.

[45] Greiner stated that UB is working "to play a larger role" in the University Heights area, but that a partnership must exist.

[45] Greiner served as UB's 13th President[15][16][17][18][49][50][51] for 13 years before stepping down in 2004[28] and returning to the role of Law Professor, retiring in 2009.

[2][7][8][18][50] In 1995, Greiner received the Medal Merentibus, the highest honor issued by the Jagiellonian University in Kraków, Poland, for his efforts in broadening the educational partnership between both institutions.

[18][56] In 2004, both Bill and his wife, Carol, were honored at a UB Alumni Association dinner with the Dr. Philip B. Wels Outstanding Service Award.

[56] In 2007, Retired Starbucks Chief Executive Officer Orin C. Smith donated $200,000 to the UB Law School in honor of Greiner.

[64] The Buffalo News quoted the letter, stating, "I do not know if it is a violation of state law or university policy to use university facilities to support the activities of a private club that discriminates against women, but it strikes me, at the very least, as a wildly inappropriate violation of judgment and good taste.

"[64] Greiner co-wrote The Nature and Functions of Law with Harold J. Berman (1918–2007) of Harvard University and Samir N. Salima of Emory and Henry College.

[2][7][8][18][20][66] Of Bill's death, his wife, Carol, stated in Buffalo Business First, "We are saddened for the future generation of UB students who will never get to benefit from his knowledge and teaching, and his gift as an educator.