You can't... which is why all the county sheriffs are against it.
You sure about that?
Check out this little quote near the bottom:
Larimer County Sheriff Justin Smith has urged state legislators to fill what he sees as a safety loophole and require gun owners in Colorado to register their firearms with the government.
Hey Larimer County, time to change sheriffs...
Update: HiBC clarifies that this was a misquote below:
Keep calling and writing your senators.