 As of March 2020, California, Massachusetts, Washington, Michigan, Ohio, and Rhode Island had passed laws banning the use of battery cages, and the former three additionally banned the sale of eggs produced in battery cages.Michigan's ban of battery cages and the sale of non-cage-free eggs in the state, adopted in November 2019, will enter into force at the end of 2024.The passage of California Proposition 2 (2008) aimed, in part, to reduce or eliminate the problems associated with battery cages, by setting the standard for space relative to free movement and wingspan, rather than cage size.