In United States v. Mathur, 685 F.3d 396 (2012), the Fourth Circuit first held that Padilla v. Kentucky announced new law and, generally speaking, would not, therefore, enjoy retroactive application.
The opinion then rejected Mathur's argument that he qualified for one of the two special exceptions to non-retroactivity, those special exceptions not being pertinent to the present discussion.
Mathur then argued that the Padilla opinion itself proclaimed its own retroactivity.
In rejecting that contention, Judge Niemeyer pointed out:
Unable to direct us to a prior case that has found that Padilla created a new right that is retroactively applicable to cases on collateral review, Mathur argues that Padilla itself can be read to hold that its new right should be retroactively applied, even though it never said it was doing so, nor did it conduct any Teague analysis as would be necessary to do so.
.. Nowhere does the opinion make a single reference to Teague and its progeny, nor to the principles annunciated in those decisions. ... The only way to make a new rule retroactive "is through a holding," not through dictum. (685 F.3d at 401).