"Common Law Wife" is a song by the funk band Parliament. Recorded in 1972, it was released as a bonus track on the 2003 reissue of the album Chocolate City. The song's lyrics discuss a relationship recognised by the state but not officiated by a religious order.
The context of the album is discussion of life and politics in Washington D.C., United States, and so it may be presumed that the relationship in question is one recognised under laws within the USA.
"Common Law Wife" was also recorded by a female artist named Flo. Her version is featured on the George Clinton Family Series CD Plush Funk, which was released in 1992.
References
Common Law Wife Wikipedia(Text) CC BY-SA