Function AllowPlayerTeleport enable/disable the teleporting ability for a player by right-clicking on the map
This function, as of 0.3d, is deprecated. Check OnPlayerClickMap
This function will work only if AllowAdminTeleport is enabled, and you have to be an admin.

(playerid, allow)
int playerid The ID of the player to allow teleport.
bool allow 1 - allow, 0 - disallow.

Return Values:
This function does not return any specific values.

public OnPlayerConnect( playerid )
    // Allows the Player to teleport by right-clicking on the map
    // since this is in OnPlayerConnect, this will be done for EACH player
    AllowPlayerTeleport( playerid, 1 ); 

Related Functions
The following functions may be useful, as they are related to this function in one way or another.