It's not only for citizens of Canada; the charter would apply to anyone in Canada. Section 10(a) of the Canadian Charter of Rights and Freedoms would indicate that one is to be advised of the reasons for one's detention or arrest immediately upon that transpiring. There's a line of cases that would support this view.
It's distinct, in effect, from the right to counsel, which is to be provided without delay. The right to know the reasons for one's detention or arrest is framed positively and should happen almost instantaneously upon arrest or detention.