Here's a question: are all laws written down?
Are they written in stone?
Well, when it comes to international law,
some are but many aren't.
Let's start with the easy one.
The written laws are usually what we call 'treaties'.
These are documents that countries sign, a bit like a contract.
We also call them things like 'conventions' or 'protocols',
like the Geneva Convention or the Kyoto Protocol.
But – what about the rules that aren't written down?
Well, you know the term 'unwritten rule'?
We might say there's an unwritten rule
that you should say sorry if you bump into someone,
or give up your seat for an elderly person.
Countries also follow unwritten rules.
We call them 'customs' or 'norms'
and they give us the legal term 'customary law'.
This covers things that most countries already believe,
like not invading another country.
All states in the international community
have to stick to customary law,
even if they haven't explicitly said yes.
And many customs do eventually get written down,
such as those in the UN Charters.