It is not that easy. There is a ton of authority that says that pardons are not entitled to full faith and credit. Consider this quote:
The courts that have considered this issue are united on certain principles. First, it is agreed that the constitutional full faith and credit clause, Art. 4, § 1, does not reach the question of what effect federal entities must give state pardons. United States v. Matassini, 565 F.2d 1297 (5th Cir. 1978); United States v. Sutton, 521 F.2d 1385 (7th Cir. 1975); Thrall v. Wolfe, 503 F.2d 313 (7th Cir.), cert. denied, 420 U.S. 972, 95 S.Ct. 1392, 43 L.Ed.2d 652 (1975).
Yascovone v Bolger, 645 F2d 1028 (DC Cir 1981). Note: every case I am citing is available on Google Scholar (scholar.google.com).
Moreover, a state has to treat another state's ruling the same as it treats its own. For example, a state which does not have legal gambling would not have to enforce a judgment for an unpaid casino debt entered by a Nevada court.
Tennessee does not restore the right for former offenders convicted of drug offenses to own firearms. Georgia does. Tennessee pardon's don't fully wipeout/expunge a criminal record; Georgia's do. Tennessee's pardons are issued by the Governor; Georgia's are issued by a Pardon Board. Georgia is probably more liberal about granting pardons than Tennessee is.
The area of wiping out/rehabilitating former offender rights is very different from state-to-state both in theory and practice and DA's/cops don't like it when a former offender gets rights back (records cleared) where a similar clearance wouldn't take place in their home state.
California expungments don't restore firearm rights and California has a history of ignoring out-of-state pardons. Here is a link to a 1974 decision refusing to recognize a Montana pardon restoring firearm rights. Federal statutory law changed in the interim. Congress has mandated that a state restoration of firearm rights will be honored. The discussion about pardons (and expungments) is therefore relevant:
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Here are a few more similar cases:
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Here is a case that says that state expungment (expunction) laws are entitled to even less respect than a full pardon:
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I'm only tossing this in the mix in case someone is thinking that the OP was talking about an expungment, not a pardon. (Some states call them expunctions). The law on the two beasts is generally the same -- it is a state act of grace given to an individual who has demonstrated rehabilitation so that they can restart their life. In fact, the Supreme Court precedent on this point (Dickerson v. New Banner Institute, Inc., 460 U.S. 103, 103 S.Ct. 986, 74 L.Ed.2d 845 (1983)) ruled that a state expungment was not binding on the federal government. The Dickerson Court noted: "an expunction under state law does not alter the historical fact of the conviction, . . . as does positive or `affirmative action'. . . . [E]xpunction does not alter the legality of the previous conviction and does not signify that the defendant is innocent of the crime to which he pleaded guilty."
There have been cases where individuals are innocent of the federal felon in possession law, but still guilty of it under state law.
My general advice to clients with pardons and/or expungments is not to travel out-of-state with the weapons. If they refuse to follow this advice, I recommend they get a CPL (even for long guns) because of the additional reciprocity arguments they can make and because it might pause the cop.
Unrelated to firearms, but while I am on the topic -- be very careful checking the "no box" to the federal government about whether you have ever been convicted an offense. As the Dickerson quote demonstrates, the feds can look through it. For example, I go to Canada alot (sans gun) and got a Nexus card to go through the expedited clearance lane. Nexus defines "conviction" to include expunged or pardoned convictions. They want to know about them, but I think they still will give you the card at the end of the day at least they do with Canadian pardons.
Unfortunately, this is a trick bag. Anyone with a sheltered, expunged, rehabilitated, or pardoned conviction has to really be a lawyer to know when and how much they can rely on the pardon. As one of my earlier posts demonstrates, even being a lawyer doesn't mean that you are always right. If I trusted Congress, I would suggest that we needed a uniform law addressing the issue, but I don't trust them on this for obvious reasons.
Stu