In May of 2003, the Senate considered House Bill 2579. The bill was about secret compartments in cars. Quickly the bill was completely gutted and replaced by language criminalizing the acquisition of more than one handgun in a thirty day period.

Obama felt this to be a particulary important piece of legislation and goes on for more than a page about this "very measured, modest regulation" starting on page 120 of the day's transcripts.

Obama voted for House Bill 2579, as amended. The bill failed to pass the Illinois Senate. 

Before that was Senate Bill 1614 in the 91st General Assembly.  It made buying more than one handgun in a thirty day period a class-4 felony. Obama was a supporter of the bill.