Leges Genuciae (also Lex Genucia or Lex Genucia de feneratione) were laws passed in 342 BC by Tribune of the Plebs Lucius Genucius.
These laws covered several topics: they banned lending that carried interest, which soon was not enforced; they forbade holding two magistracies at the same time or within 10 years; and lastly, they required at least one consul to be a plebeian.
The first time both consuls were plebeian was in 172 BC. By then, that provision was the only one that continued to be enforced.
References
Leges Genuciae Wikipedia(Text) CC BY-SA