Sounds like a statute that can and will be easily ignored.
It is. In Colorado estimates are that only 13% of private gun owners complied and there have been zip, zero, nada successful or even attempted prosecutions for violations of the law. The reason is that it is virtually impossible for law enforcement to prove when a private sale or trade took place assuming there is no check, receipt or other dated record to prove the transaction took place before or after the law changed.