US v Stallings involves a federal life sentence
enhancement under 21 USC 841(b) based on prior felony convictions from Nevada and California. The federal court
of appeal held that the California prior was not properly proved and therefore should not have been used to enhance the defendant's sentence.
Federal sentencing laws have no application to sentencing in New York state cases, so Stallings will have no effect on a current New York case. Nor does it help determine which code section applies in the case you are concerned with because that is a factual issue, dependent upon what drugs were involved and what charges were filed.
New York does have persistent felony laws which authorize similar enhancement for prior felonies. They are contained in Penal Code section 70.10 and Criminal
Procedure Code section 400.20 and authorize extended imprisonment and lifetime supervision upon release from prison. The New York laws do have some similarities to the federal statutes, in that the priors must be properly noticed and proved beyond a reasonable doubt.
If your concern is sentencing under the New York persistent felony statutes and the validity of priors, then going back to your original question, the answer is that priors from 2001 can be used to enhance under the persistent felony law if they are valid and meet the requirements of Penal Code section 70.10 (b), which are somewhat more stringent than the federal rules:
(b) A previous felony conviction within the meaning of paragraph (a) of this subdivision is a conviction of a felony in this state, or of a crime in any other jurisdiction, provided:
(i) that a sentence to a term of imprisonment in excess of one year, or a sentence to death, was imposed therefor; and
(ii) that the defendant was imprisoned under sentence for such conviction prior to the commission of the present felony; and
(iii) that the defendant was not pardoned on the ground of innocence ....
Note in particular that for purposes of the New York persistent felony laws, a prior can be used to enhance only if the defendant was actually imprisoned on the prior. Therefore, cases in which probation was granted, sentence was suspended or imposition of sentence was suspended and no prison time was actually served cannot be used to enhance under the New York persistent felony offender law.