#include <sourcemod>   

new CBasePlayerOffs;
new bool:bIsBlock[MAXPLAYERS+1] = {false, ...};

public OnPluginStart(){
  CBasePlayerOffs =  FindSendPropOffs("CBasePlayer", "m_fFlags");

  RegConsoleCmd("cam", Command_Cam);
}

public Action:Command_Cam(client, args){
     SetEntData(client, CBasePlayerOffs, !bIsBlock[client] ? FL_CLIENT|FL_ATCONTROLS : FL_FAKECLIENT|FL_ONGROUND|FL_PARTIALGROUND, 4, true);
     bIsBlock[client] = !bIsBlock[client] ? true : false;
      
     return Plugin_Handled;
}