The Supreme Court opted Monday not to take up a challenge against a ban on so-called assault weapons in the state of Maryland.

This decision effectively allows the state law to remain in force. Maryland enacted the ban following the Sandy Hook Elementary School massacre in 2012, in which an assailant armed with an AR-15 killed twenty children and six adults.

Three conservative Justices publicly indicated they would have accepted the case, while a fourth has previously expressed skepticism about the constitutionality of such prohibitions, suggesting the Supreme Court might eventually address the issue.

What exactly constitutes an “assault weapon” remains disputed territory. Generally speaking, the term is used by progressives in reference to semiautomatic firearms capable of accepting detachable magazines, though this definition varies widely in application.

Several states have implemented comparable restrictions in recent years, and Democrats in Congress have consistently backed these measures, but with minimal success.

Second Amendment advocates meanwhile note that citizens have a constitutional right to possess firearms like the AR-15. The federal ban on so-called assault weapons, which expired back in 2004, primarily targeted certain cosmetic features rather than the underlying weapons themselves.

The prohibition in Maryland stands for now, and the legal challenges are likely to continue as the contentious debate over gun control persists.