 As a modern workaround for the first sale rule, many online content providers, rather than selling a copy of a work, simply offer licensing agreements (through click-wrap, shrink-wrap, etc.) that allow only specific uses of protected content. These approaches to protecting intellectual works are relatively new and seemingly build upon the copyright systems already in place. For example, by using licensing agreements to guarantee different levels of downstream access, the Creative Commons and Copyleft models seek to expand the commons of thought and expression (Stallman 1997; Lessig 2004). An owner may allow others to build upon a protected work provided that the “new” work is similarly accessible or usable. Note that the moral bindingness of these contracts/agreements presuppose prior entitlements (hinting at the moral justifications offered below). For example, if neither party to a Copyleft license owns or has legitimate title to the intellectual work in question, then the resulting agreement/license will not be binding. Thus, Creative Commons and Copyleft models are actually built upon ownership or entitlement claims to intellectual works.