We are working on the retroactive application. For now, think about the prospective use of Brooks because prior felony convictions have far-reaching and serious consequences.
A couple of examples:
Under USSG 2K2.1(a)(1)-(4), the base offense level for felon-in-possession increases for one or more prior convictions for certain felonies. A Kansas conviction for those offenses may not qualify if the client did not face a sentence of greater than 12 months. Moreover, under (b)(6), a four-level enhancement can apply if the weapon was used or possessed "in connection with another felony offense." The offense must be specified, and under Brooks may not be a felony.
Think about supervised release violations, too. The grade of the violation, as defined by USSG 7B1.1, determines the guideline range. Both Grade A and B violations may consider conduct that constitutes a felony -- an "offense punishable by a term of imprisonment exceeding one year." Again, that conduct must be identified. If it happens to fall into a grid box where the top number is 12, your client falls from a Class A to a Class C violation.