Firstly in response to your other review.
1. SkLib is outdated and the vpn condition does not work.
2. It's a tiny command, sure, else if's are good advice, but it shouldn't downvalue his resource to 1 star.
3. Using a filter is essentially the same as looping all players.
There are much bigger problems with this script than the things you mentioned, and one star is far too harsh for the things you said.

Back to the resource, here are some valid reasons why it is a bit broken. This would work fine as an antivpn PROVIDED the player thats joining has a static ip address, doesn't move house or change network providers, and they don't originally join on an vpn.
You can improve this a lot in the future by using databases of known vpn ip addresses to crossreference the player but there are resources that already do this.
You should also use list variables.
You also do not set a variable in this script which means nobody can join.
You also need to include an if section in your command for incorrect syntaxes otherwise it will say nothing.
Good attempt though I hope you learn from this! :)

First of all, skLib has a literal condition for this ( https://skripthub.net/docs/?id=1181)
Second, instead of else ifs you use multiple ifs and stop triggers which is a waste of lines
Third, instead of looping all players use
send "" to all players where [input has permission "antivpn.staff"]