Don’t even need a new lawsuit...the lower court enforcing Heller will strike down DC’s new try.
Heller is one of the most important SCOTUS decisions in 225 years is because it puts gov't entities (right now, DC, but after Chicago ie incorporation, the entire US) on defense.
What this means is the minute any new law/regulation is signed, a motion for injunction will be filed, and granted. NOTHING will be implemented until the law is overturned.