iirc you can marry a first cousin by common law marriage in alabama. in fact the code of alabama doesn't specifically prohibit any ~Relations~ with cousins
First-cousin marriage is legal in the UK.
It's the only blood-related marriage that is.
According to wikipedia, over 10% of all marriages world-wide are cousin marriages.
In fact, first-cousin marriage is legal in most of the world.

Dark Blue is legal.
Light Blue is legal, with restrictions/exceptions.
Orange is legal, depending on religion/culture.
Red is banned by statute.
Pink is banned, with exceptions.
Dark Red is a criminal offence.