Discrimination in employment in non-federal positions is governed by provincial non-discrimination statutes. Saskatchewan's Human Rights Code says that (s. 19):
No person shall use or circulate any form of application for employment
to which this Act applies, publish any advertisement in connection with that
employment or prospective employment, or make any written or oral inquiry or
statement in connection with that employment ... that expresses, directly or indirectly, a limitation, specification or
preference indicating discrimination or an intention to discriminate on the
basis of a prohibited ground
"Prohibited ground" includes "gender identity."
The language quoted in the question is a standard way to express a preference for women. Thus, on its face, the advertisement is in violation of s. 19 of the Code.
However, s. 55 provides for pre-approved hiring "programs":
if the program
is designed to prevent disadvantages that are likely to be suffered by, or to eliminate
or reduce disadvantages that are suffered by, any group of individuals when those
disadvantages would be or are based on or related to the race, creed, religion, colour,
sex, gender identity, sexual orientation, family status, marital status, disability, age,
nationality, ancestry or place of origin of members of that group, or the receipt of
public assistance by members of that group, by improving opportunities respecting
services, facilities, accommodation, employment or education in relation to that
group or the receipt of public assistance by members of that group
The Saskatchewan Human Rights Commission has explained that these "programs" can include even a single contract entered on a preferential basis to achieve the goals of s. 55.
There are many examples of targetted hiring being approved under s. 55 (or the former s. 47). For just one reported example, see Regina (City) (Re), 81987 CanLII 8554 (Sask. H.R.T.), which approved an affirmative action hiring program targetting "persons of [Indigenous] ancestry, persons with physical disabilities, and women."
I obviously cannot know whether the advertisement you quote from the University of Regina flows from an approved program, but I can say it would not be out of the ordinary if it did, and they had an approved program as far back as 2002.