The Justice Department filed a lawsuit against Missouri on Wednesday in an attempt to stop officials from enforcing a bill that would ban local police from following federal gun laws that the state declared "invalid."

Why it matters: It alleges that Missouri's Second Amendment Preservation Act is unconstitutional and hindering law enforcement efforts in a state where "nearly 80% of violent crimes are committed with firearms," per a Justice Department statement. Missouri officials vowed to fight the suit, which they say attacks Second Amendment rights.

Driving the news: The bill, which was signed into law last June, penalizes federal, state and local law enforcement officers for enforcing federal laws, according to the Department of Justice.