Here's what I did:
I used a teledoor, and set the evets to the following (Requires VCE)
onTeledoorEnter > Self > VCE_retrocheck > ifAdmin
onVariableFalse > Player > InstantRespawn
This way, if a non-admin tries to get in, they'll be instanltly respanwned.
I know this is like this person's idea:
[Onplayertouch] [self] [VCE_retrocheck] [ifadmin]
[onvariabletrue] [namedbrick] [brick B] [setplayertransform]
Or you could do this:
Place a 4 x 4 brick in front of a door and put in the following events:
onPlayerTouch > Self > VCE_retrocheck > ifAdmin
onVariable False > Player > InstantRespawn
-or-
onVariableTrue > self > ContentStart (The instantrespawn prevents any unwanted players to go thru the door)