Because a criminal who broke the law by having a gun will obey ‘saner’ gun laws.
The dirty secret is that this violent felon had been arrested 39 times prior to committing murder in Chicago and the Illinois criminal justice system had allowed him back on the streets!
Illinois jails and prisons are revolving door institutions: no one serves full sentences; the death penalty has been abolished; judges are soft on criminals; Democratic politicians want to release more criminals to end mass incarceration due to systemic racism (no respect for jury trials that convicted the criminals). The bitter truth is that the crooked Illinois politicians do not want to pay to keep prisoners locked up because it costs about $150.00 per day, so they let’ em go.