Washington ( CNN ) -- President Obama signed a bill Tuesday reducing the disparity in penalties for the use of crack and powder cocaine , according to the White House . The enactment of the law seals a hard-fought victory for civil rights activists who have argued for years that the differing punishments unfairly target African-Americans . The Fair Sentencing Act repeals a five-year mandatory sentence for first time offenders , and for repeat offenders with less than 28 grams of crack cocaine . The old law set the mandatory sentence for conviction at five grams . African-Americans have been far more likely than whites and Hispanics to be convicted for -- and receive the harsher penalties associated with -- possession of crack cocaine , according to government statistics . White and Hispanic defendants are more frequently charged with possession of powder cocaine . The now-defunct measure had been in place for 25 years . The House passed the new law through a bipartisan voice vote last week , following approval by the Senate in March . Support for reducing the disparity with powder cocaine offenders increased with reports beginning in 2002 by the U.S . Sentencing Commission calling for Congress to change the crack cocaine law . The commission is an independent agency in the judicial branch that develops national sentencing policy for the federal courts . Rep. John Conyers , D-Michigan , recently contended that the new law will reduce sentencing disparity between crack and powder cocaine from 100-to-1 to 18-to-1 . Conyers said crack mandatory sentences had pushed the number of drug offenders in federal prisons from fewer than 5,000 in 1980 to nearly 100,000 in 2009 . Obama and Attorney General Eric Holder had both publicly pressed for passage of the new statute . `` This day was long in coming , '' Holder said recently . The attorney general claimed the bill will `` go a long way toward ensuring that our sentencing laws are tough , consistent , and fair . '' Members of the Congressional Black Caucus had led the battle for passage for 10 years , but several key Republicans -- including Alabama Sen. Jeff Sessions and South Carolina Sen. Lindsey Graham -- also pushed for the change . House Republicans Dan Lungren of California , James Sensenbrenner of Wisconsin , and Ron Paul of Texas also provided high-profile support . Not all Republicans joined the majority , however . The top Republican on the House Judiciary Committee Lamar Smith , R-Texas , argued vigorously shortly before passage that to reduce the crack cocaine penalties would be a serious mistake . `` Reducing the penalties for crack cocaine could expose our neighborhoods to the same violence and addiction that caused Congress to act in the first place , '' Smith said . `` Crack cocaine is associated with a greater degree of violence than most other drugs . And more than any other drug , the majority of crack defendants have prior criminal convictions . '' CNN 's Terry Frieden and Alan Silverleib contributed to this report .
NEW : Blacks more likely than whites , Hispanics to be convicted for crack cocaine . Crack cocaine sentences were more severe than those in powder cocaine cases . Attorney General Eric Holder : `` This day was long in coming '' Some key Republicans backed the new law , but others warned it is a mistake .