The Volokh Conspiracy covers and interesting case today. The Jacson county Sheriff in Oregon had denied a concealed carry permit to a Oregonian who was a medical marijuana user on the basis that the Federal law prohibiting such users from possessing a handgun preempted the Oregon state law.
The Court of Appeals upheld the the circuit court's reasoning that the CHL does not permit a person to carry a handgun - that right flows from the Oregon constitution. All the CHL does is remove the criminal liability from carrying one concealed. As a result, issuance of a CHL is not in conflict with Federal law and the Sheriff must issue the permit.
Interesting angle.