There are 2 things.
1) Against the law, you can get sued. Illegal. Allowed.
2) Against server rules. You can get punished. Not Allowed.
Scamming is not allowed in the following:
Any legal deal
House or business sale
Scamming new player for whatever reason
Scamming on a bet inside a casino
Scamming on a weapon deal inside the ammunation
Scamming in drug deals, in loans, in weapon deals(outside ammu) in blackjack or 2x, outside the casino is against law. This means you can get suspected and arrested by cops but you will not be punished.
Scamming I'm all illegal trades is allowed, but since it is illegal, you can get arrested by the cops.
Scamming in loans is also not against server rules, but you can get sued in court for it. Meaning the guy may get his cash back by using you in court, but you won't be banned or punished.