The appellants submit that this court in Brown “did not
dictate that the police officer must arrest the ‘angry crowd’ or
individuals who are threatening harm or being provoked into
violence”. Indeed, it did not. But nor did Doherty J.A. endorse
the arrest of individuals exercising Charter-protected rights and
freedoms as a first step in seeking to preserve the peace. On the
contrary, he was careful to emphasize that the necessity of taking steps to preserve the peace arises only when there is a real
risk of imminent harm. “Before that point is reached”, he wrote,
at para. 78, “proactive policing must be limited to steps which do
not interfere with individual freedoms”.
 This last point bears repeating: “proactive policing
must be limited to steps which do not interfere with individual
freedoms”. There is no doubt, as Doherty J.A. acknowledged in
Brown, that the protection of rights and freedoms makes crime
prevention and peacekeeping more difficult for the police; it
may even preclude the police from preventing crime. But that
is the price that must be paid if rights and freedoms are to
(b) Was Mr. Fleming’s arrest necessary?
 In order to justify the use of the common law police
power to arrest Mr. Fleming, the appellants must show that
“the police action [was] reasonably necessary for the carrying out
of the particular [police] duty in light of all of the circumstances”
(emphasis in original): MacDonald, at para. 36.
 This is the key question on appeal — whether or the
extent to which it was necessary to interfere with Mr. Fleming’s
liberty in the circumstances. This depends on whether a breach
of the peace was “imminent” and there was a “substantial risk”
that it would occur. As Doherty J.A. explained in Brown, at
para. 74, “[t]he mere possibility of some unspecified breach at
some unknown point in time will not suffice . . . the police officer
must have reasonable grounds for believing that the anticipated
conduct . . . will likely occur if the person is not detained”. The
“imminence and substantial risk” test has been endorsed by
this court in R. v. Baker (2004), 73 O.R. (3d) 132,  O.J.
No. 4102 (C.A.), at para. 20; and Figueiras v. Toronto (City)
Police Services Board (2015), 124 O.R. (3d) 641,  O.J. No.
1515, 2015 ONCA 208, at paras. 98, 120.
 The trial judge found, at p. 43, that “it is not clear from
the evidence that the natural consequence of Mr. Fleming
walking up a street in Canada with a Canadian flag, and then
walking onto and standing on land owned by the province would
provoke others to violence, so as to establish an actual danger to