Cook County, Illinois, and Massachusetts both have assault weapons bans in place. These bans are based on a national assault weapon ban that expired in 2004 when Congress did not renew it. Cook County enacted its ban in 2007. The Massachusetts ban has been in place since 1998. Cook County’s ban charged large fines to people owning certain types of guns without authorization. On July 20, 2016, the Massachusetts Attorney General released an Enforcement Notice providing guidance on the details on the ban. These bans refer to assault rifles like the AK-47 and AR-15.

Cook County State's Attorney Kim Foxx was happy about this decision by the Supreme Court, saying, “Today's Supreme Court decision was a huge victory in the battle to keep our communities safe and dangerous weapons off the streets." Later, she added, “We will continue to use the power of this office as we work for justice and fairness for everyone in communities across Cook County."

Some of the guns banned under the Massachusetts ban include “copies” or “duplicates,” which are defined as “The weapon’s internal functional components are substantially similar to the construction or configuration of a weapon that is expressly banned under the law (such as a Colt AR-15 or a Kalashnikov AK-47)” or “The weapon has a receiver that includes or accepts key operating components that are interchangeable with those of a banned weapon.”

The NRA tried to bring cases against these bans to the Supreme Court. However, the Supreme Court declined to hear either case. There are two plausible reasons that the Supreme Court refused to hear the cases. Either they believe that it is an issue that should be left to the state or local government to decide or they agree with the ban currently in place in those jurisdictions. There are many arguments for and against banning assault weapons.

An argument that many people bring up for gun bans is to stop mass shootings. However, men who carry out mass killings often use handguns. Also, a person who wants to carry out a mass shooting will not just accept defeat and not go through with the shooting just because he cannot get an AK-47 or AR-15. He will find another type of gun. Assault rifle bans will not guarantee the ending of mass shootings. They are just put in place hoping that the mass shootings will stop. These bans also will not take away the guns from those who already have them; they only prohibit new sales. Additionally, most gun deaths are suicides. There have been no studies to determine whether a ban like this would help curb the number of suicides. Bans on assault weapons have furthermore not been shown to decrease violent crime. California enacted a ban on assault weapons in 1989 and then saw an increase in their murder rate for five years in a row.

In contrast to those arguments, the Washington Post did an investigation on the effects of the federal assault weapons ban in Virginia. While this ban was in place, “there was a noted decline in the number of guns equipped with high-capacity magazines recovered from crime scenes; the rate reached a low of 10 percent in 2004. After the ban expired, this rate increased, reaching 20 percent in 2010.” The Washington Post researched mass shootings over a 35-year period. During the time that the federal ban on assault weapons was in place, the number of mass shootings went down 25 percent and the number of gun deaths due to mass shootings went down 40 percent.

Assault weapons bans are a hotly debated topic within the broader gun rights debate. With the federal ban on assault weapons no longer in place, it is now up to the states to decide whether they want to implement or enforce their own bans. Meanwhile, a changing judiciary might further embolden gun rights advocates to continue to bring challenges to assault weapons bans and other gun control laws in the federal courts.