The closest thing the River Kingdoms have to a unified set of laws is the code of justice known as the Six River Freedoms. They are normally ranked in ascending order of importance. Thus free speech is not considered as important as freedom from slavery, for example.
Say What You Will, I Live Free
This is the freedom of speech (and not to be confused with freedom from the consequences of your words). Criticism of government is common in the kingdoms, and lords of the kingdoms who are lenient with loose tongues are likely to live longer.
Making an oath is a huge deal for the people of the River Kingdom (where trust is hard to come by and earned in blood), and this freedom grants the people of the kingdoms leave to persecute anyone person that breaks an oath. Riverfolk who take on oaths usually keep them, or die trying.
This freedom can have some constricting side effects on traders and businessmen, who are loath to make strict commitments or promises.
Walk Any Road, Float Any River
This freedom prevents lords of the river kingdoms from blocking travel over land and water, including charging tolls for passage. In particular, this means that no lord may own the mighty Sellen River, although it also means that every river barge is its own kingdom with its captain being the king.
Courts Are For Kings
One of the most basic freedoms of the River Kingdoms, this one holds that all laws within a river kingdom are flexible, and that rulers of a kingdom may do as they wish. Visitors to a river kingdom —be they king or commoner—are bound by the (often arbitrary) laws of that kingdom. Consequently, rulers of the different kingdoms infrequently visit each other, and instead rely on liaisons and intermediaries. The exception to this is the annual Outlaw Council, which is considered neutral ground for everyone.
Slavery is an Abomination
Escaped slaves are an important fact of life in the River Kingdom. A slave that escapes to the River Kingdoms is considered truly free. By some estimates, more than a third of all people living in the River Kingdoms are either escaped slaves or children of escaped slaves. Thousands of slaves make their way to the River Kingdoms annually and fiercely defend their newfound freedoms.
Hellknights of the Order of the Chain, or members of any other slaving organization, are unable to hold office in the River Kingdoms, and Andoran Eagle Knights are held in special regard by its people.
You Have What You Hold
This freedom draws the moral distinction between burglary and robbery. Burglary, or the taking of another's property without their knowledge, is considered offensive and is punishable under common law, as it robs the victim of the ability to defend him or herself. In the River Kingdoms it is more preferable to face your robber, to be allowed the opportunity to resist (and perhaps to repossess!). It is acceptable (and perhaps worthy of praise) to take what you want by force.
- Erik Mona et al. (2008). Campaign Setting, p. 129. Paizo Publishing, LLC. ISBN 978-1-60125-112-1
- Jeff Quick. (2010). The River Kingdoms. Guide to the River Kingdoms, p. 8. Paizo Publishing, LLC. ISBN 978-1-60125-203-6
- Tim Akers et al. (2014). People of the River, p. 21. Paizo Inc. ISBN 978-1-60125-666-9
- Kevin Andrew Murphy. (2010). The Fifth River Freedom (Prodigal Sons). Blood for Blood, p. 71. Paizo Publishing, LLC. ISBN 978-1-60125-251-7
- Brock Mitchel-Slentz. (2010). Heibarr. Guide to the River Kingdoms, p. 20. Paizo Publishing, LLC. ISBN 978-1-60125-203-6