Adam Liptak has this story in the NYT on the cases (see update below):
Selling cocaine in crack form used to subject offenders to sentences 100 times as long as those for selling it in powder form. The new law, the Fair Sentencing Act of 2010, reduced the disparity to 18 to 1, at least for people who committed their offenses after the law became effective on Aug. 3, 2010.Um, no. It wasn't the sentences that were 100 times as long. The controversial "ratio" refers to the amount of cocaine that triggers the longer sentence, as indicated later in the story. (See also this post.)
The usual rule is that new laws do not apply retroactively unless Congress says so, Judge Evans wrote, and here Congress said nothing.
Edward Dorsey pleaded guilty in June 2010 to possessing 5.5 grams of crack cocaine in 2008 with the intent to distribute it. Under the law in effect at the time of his offense and his plea, and thanks to an earlier conviction, he was subject to a mandatory minimum sentence of 10 years. Under the new law, the mandatory sentence would not have come into play for fewer than 28 grams, and Mr. Dorsey would probably have received a sentence of three or four years.
The sentence ratio is thus 3.3 to 2.5, not 100.
Update: As federalist notes in the comments, the article has subsequently been corrected.