He didn't really walk away:

"A 24-year-old Australian man who ordered uranium and plutonium to his parents’ apartment has been allowed to walk away from court on a two-year good behaviour bond.

After ordering various radioactive samples over the internet in an effort to collect the entire periodic table, Emmanuel Lidden pleaded guilty to two charges: moving nuclear material into Australia and possessing nuclear material without a permit.

While his actions were criminal, the judge concluded that Lidden had mental health issues and displayed no malicious intent"

The court established he had mental helath issues and has 2 years probation basically.