Padilla dealt with two different IAC claims:

(1) Failure to advise of immigration consequences at plea; and
(2) Affirmatively misadvising of immigration consequences at plea.

Padilla v. Kentucky, 130 S. Ct. 1473 (2010).

The first claim is not retroactive. Chaidez v. United States, 133 S.Ct. 1103 (February 20, 2013). The second claim is retroactive. Chaidez specifically says it does not apply to affirmative misadvice IAC claims. As the court stated:

True enough, three federal circuits (and a handful of state courts) held before Padilla that misstatements about deportation could support an ineffective assistance claim. But those decisions reasoned only that a lawyer may not affirmatively misrepresent his expertise or otherwise actively mislead his client on any important matter, however related to a criminal prosecution. See, e.g., United States v. Kwan, 407 F.3d 1005, 1015"1017 (C.A.9 2005). They co-existed happily with precedent, from the same jurisdictions (and almost all others), holding that deportation is not so unique as to warrant an exception to the general rule that a defendant need not be advised of the [collateral] consequences of a guilty plea. United States v. Campbell, 778 F.2d 764, 769 (C.A.11 1985). [Footnote omitted.] So at most, Chaidez has shown that a minority of courts recognized a separate rule for material misrepresentations, regardless whether they concerned deportation or another collateral matter. That limited rule does not apply to Chaidez's case.

Chaidez, supra, at 1112. Justice Sotomayors dissent accurately points this out, and says that a plea based on mistaken legal advice has for many years been the law, when she referred to the age-old principle that a lawyer may not affirmatively mislead a client. Id. at 1113 (Sotomayor, J., dissenting).

All we have to do is to avoid a failure to advise claim (not retroactive) and reframe the
IAC claim as affirmative misadvice. For example, see an immigration lawyer after plea.
Or This plea might cause your deportation (when it causes mandatory deportation), or even simply standing by while the judge says Might cause, without correcting the mistaken advice. The attorney thereby adopts the misadvice. Look carefully at everything the lawyer did say about immigration, and at what the court said about immigration consequences, and find something wrong. See the wonderful practice advisory on Chaidez on the NLG NIP website.

Also see the Immigrant Defense Project practice advisory on litigating post-conviction relief cases in NY, where New Yorks highest court found Padilla not to be retroactive.
The strategy suggestions in this advisory may prove helpful in states where Padilla has been deemed non-retroactive. Practitioners in states where the issue has not been decided should also consider these strategies, to ensure that the arguments are preserved in the event that Padilla is deemed non-retroactive.

While Chaidez held that Padilla is not retroactive as to failure to advise claims, it left open several issues. Here is a non-exhaustive list:

(1) Perhaps most importantly, Chaidez does not bind state courts. So unless you are in a state that has affirmatively rejected all of the many arguments for retroactive application, those arguments should continue to be presented in state court.

(2) Chaidez did not decide whether a different retroactivity rule should apply where a claim of ineffective assistance of counsel is properly raised for the first time in postconviction proceedings. 133 S. Ct. 1113 n.16. That claim is quite strong and should continue to be raised in any jurisdiction that has not explicitly rejected it.

(3) Chaidez did not decide whether a different retroactivity rule should apply in federal postconviction proceedings brought pursuant to 28 USC 2255. 133 S. Ct. 1113 n.16. This argument is similar to the argument that a different retroactivity rule should govern state postconviction proceedings (an argument that has succeeded in some states) and can continue to be raised in federal postconviction proceedings.

(4) Chaidez did not decide whether the Padilla rule is a watershed rule. 133 S. Ct. 1107 n.3. So that argument is available in many jurisdictions.

Many of these arguments (or similar ones) have been presented in the amicus briefs I have filed on this issue, some of which are available here.

Thanks to Christopher N. Lasch.