This sounds like a massive violation of due process.
Edit: Also, the hearing after the fact is not a criminal case. Therefore there's no Constitutional right to counsel, jury trial, confrontation, subpoena power, public trial, presumption of innocence, burden of proof on the State, proof beyond a reasonable doubt...it's legally not that different from forfeitures. "Oh, this large amount of cash? Prove to a jaded judge that you didn't get it from illegal activity. Also you have no right to a public defender. No, I don't care if you can't afford an attorney."
The new law is not only a violation of due process, but also ripe for abuse. It's the typical "We have to do SOMETHING!" legislation made by panicky people who don't properly understand the subject that will likely be worthless in actually preventing what it sets out to do while causing problems for innocent people.
Here's a fun fact: Elliot Rodgers had kept the existence of his guns hidden from the police and his parents. This new law would have done absolutely nothing to prevent the most recent infamous mass shooting. It also would have done nothing to prevent Adam Lanza, James Holmes, Seung-Hui Cho, or the Harris & Klebold; none of these people were publicly known to be armed and few or no people had raised complaints about their behavior that would have resulted in them being arrested or stopped in any manner.
As usual, rather than combating the poor state of mental health and poor enforcement of existing laws in our nation we're attempting to use shotgun-like legislation that restricts everybody's rights in the hope that criminals and psychopaths will be caught up in it. And then when it inevitably fails to make an impact, even more laws get introduced to try and make up for it...