Any loophole is private party transfers (which could theoretically happen in the parking lot of a gun show, or any other parking lot). Which is now illegal in Oregon, but will likely not become illegal most places.
The federal law I've proposed regarding firearms restrictions on ID is the only way this could be addressed nationwide. Everthing else crosses a line for most gun rights enthusiasts, as well as Republicans in general.
However, solving the problem isn't actually a goal of democrats, so they don't like the restricted ID solution either.
If it worked they'd lose a very valuable wedge issue...