...but OK at regional winter events in BC and Alberta, provided they meet the Provincial Hwy Act definition (read: street legal studs only).
From the Rally West Regional Regulations
Section 220.127.116.11 "Tire Studs"
Studded tires may be used on Rally West events with the following limitations:
a) Studs are only allowed on events outside of Manitoba that take place from Oct 1 to Apr 30th of the following year
b) Studs are only allowed on stand-alone regional events, not on National / Regional combined events.
c) Studs must protrude no more than 3.5mm from the tread face.
d) The visible portion of each stud must be no more than 5mm in diameter, and any cross-section of the visible stud (as originally installed) must be perfectly round in shape, and must be of solid construction, not hollow.
e) The studs must be commercially and commonly available, and of conventional design, from tire dealers in the Rally West or BC regions (i.e., no homemade or specially imported studs).
f) There must be a maximum of 130 studs per tire, regardless of tire size
g) Studs must be run on all four corners the car
h) Studs cannot be replaced in, or added to any tire for the duration of the event once the tires have passed scrutineering.
i) All studded tires must be presented to the scrutineer before they can be used on an event
j) Studs are permitted in all Regional classes.