to this court to substitute its view as to the lawfulness of
Mr. Fleming’s arrest.
B. The arrest for possible breach of the peace
(1) Did the flag rally constitute an “Aboriginal Critical
 My colleague concludes that the trial judge erred in finding that the flag rally did not constitute an “Aboriginal Critical
Incident” and, as a result, that the O.P.P.’s “Framework for
Police Preparedness for Aboriginal Critical Incidents” did not
apply. He does not characterize this as a palpable and overriding
error, nor could he. Nothing follows from it: the O.P.P.’s policy
had no special status in law. Even assuming that the trial judge
erred — assuming that the flag rally was an “Aboriginal Critical
Incident” and the police were following the policy they had
established — the lawfulness of Mr. Fleming’s arrest depended
not on whether it complied with police policy but, instead, on
whether it complied with the common law police power to arrest
an individual to avoid a possible breach of the peace.
 The error my colleague attributes to the trial judge is significant, however, because it reinforces the subtext of his decision: the trial judge erred in determining that Mr. Fleming’s
arrest was unlawful because, in his view, she failed to defer to
the operational decisions of the police and failed to appreciate
the circumstances at Caledonia, in particular the history of conflict. Nordheimer J.A. specifically disagrees with the trial judge’s
statement that the lawfulness of Mr. Fleming’s arrest must be
determined based on the police actions on May 24, 2009, the
date of his arrest. This, he says, wrongly compartmentalizes
the history of the conflict at Caledonia; the steps taken by the
police on that day were necessarily and properly informed by
the history of that conflict.
 The difficulty with this position is that, as outlined below,
the police power to arrest for a possible breach of the peace
depends on an evaluation of the circumstances existing at the
time of the arrest. Those circumstances are, of course, informed
by the relevant history. But the legality of an arrest depends on
whether a breach of the peace is imminent and the risk that the
breach will occur is substantial, and those determinations must
be made based on extant circumstances. It cannot be assumed
that a history of conflict justifies the exercise of police power in
all future circumstances.
 In any event, it was not contested that the level of conflict
had decreased in the years since the occupation of DCE began.