if(strcmp(cmdtext, "/po", true) == 0)
{
 if(IsACop[playerid] == 1) //your check for a cop
 {
   //assuming its for roleplay...
   for(new i = 0; i<MAX_PLAYERS; i++)
   {
    new Float:x, Float:y, Float:z;
    GetPlayerPos(playerid, x, y, z);
    if(PlayerToPoint(50, i, x, y, z))
    {
      SendClientMessage(playerid, color, "**A nearby cop shouts PULL OVER NOW!!!");
    }
   }
   return 1;
 }
 else
 {
   SendClientMessage(playerid, color, "Not allowed to use this command!");
 }
 return 1;
}