You can't just say "No loopholes". Because the loophole existing means the original rule was never broken. A loophole is essentially "Not breaking a rule". If you say "No loopholes", then what exactly would define a loophole as a loophole? Would you just say everyone's guilty?
It all depends on where we're defining this rule.
When it's on some internet server, you can typically just ban someone for any or no reason, as long as you write it up in the TOS.
When it's in the law, it's a really bad idea. It's a better idea to just expand on the existing laws. You wouldn't want to get someone in trouble for using a 'loophole' when they're really innocent. At the same time, someone might find a loophole to avoid the loophole law!
So really, it's just bad I guess.