[Jarnu]

Using a variable and 'if' statement.

Example:

pawn Код:

CMD:whatever(playerid, params[])
{ 
    if(!IsPlayerAdmin(playerid)) return SendClientMessage(playerid, 0xFF0000FF,"ERROR: You are not admin!");  //You can change IsPlayerAdmin to your variable
   //Your codes
   return 1;
}

IsPlayerAdmin is default sa-mp RCON administrator check. This will check if the player is an RCON administrator.
You need to create your own variable to make this, i prefer you should check some of admin scripts on this forums.