The decision in united states v. lopez (1995) was particularly important because it required congress to

It required the congress to rewrite the gun free school act.

This is because the gun free school act of the time was connected to the commerce section of the constitution and it was ruled to be unconstitutional. They had to change it to remove that part and base it on something else. The new act that war rewritten is in use to this day because the old one had the loophole of commerce.