There's probably 2 ways, but first will only spectate, and second can be made to kick.
First way
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Make layout on your track(s) using SHIFT U and place the restricted area/invisible marshall red circles where you don't want drivers to go.
This would be the easiest way, as you don't have to know any Insim/language skills, and it's a very easy graphical way of seeing what you're doing.
Personally, I think kicking someone for entering a restricted area a bit severe, but if they do enough times, maybe they'd get fed up and leave your server.
Second way
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Using LFSLapper, define a zone that you want to be restricted, and then add subroutine to that zone that kicks the driver(s) that entered the zone.
Bit harder, as you'd need to learn a little about coding lapper to suit, although there are zone examples that you can change.
You would also have to manually find each of the area's you wanted to restrict access to and locate the zone (done thru lapper's !zone command).
For instance.
I use lapper zones for displaying various messages, e.g. leaving pits, entering pits, speedtraps, etc.
If I wanted to show everyone a warning message when leaving Blackwood pits, I would have;
RegisterZoneAction( "BL1" , 12,591, 3 , SE_leavepits );
BL1 is the track, 12 + 591+ 3 are the zone criteria, and SE_leavepits is the sub-routine.
My sub-routine would look like;
Sub SE_leavepits( $userName ) # A Sinanju Event
$NickName = GetCurrentPlayerVar("NickName");
openPrivButton( "remember",138,52,44,8,6,8,32,"Remember", $NickName );
openPrivButton( "leavepits",138,66,44,5,4,8,16,"Watch for traffic when exiting pitlane" );
EndSub
To kick someone, you just need to add the following line at bottom of your sub-routine (before 'EndSub');
cmdLFS( "/kick " . GetCurrentPlayerVar("UserName" ) );
Good thing is, you can set up multiple zones, but you only need the one sub-routine.
However, like I said, bit harder, but could be done.
Although learning to use lapper likely to be easier than trying to learn a lot of the programming languages (but maybe not as useful).
Really down to you and how much effort you want to put into it.
Doubtful if anyone else will put the effort in for you.
Good luck.
