The Terminator 2: Judgment Day actor was remanded to prison last week for allegedly violating a protective order filed by his girlfriend.
Furlong's probation was put in place in 2010 when his ex-wife Rachael Kneeland also filed a restraining order against the star.
His attorney Brian Michaels has now spoken out to E! News to explain why Furlong will spend the next several months behind bars.
Michaels commented: "Despite the best efforts of my office, and with the cooperation of the City Attorney and the Court in this case, Mr Furlong had the opportunity to avoid jail in a deal my office worked out, which would have resolved not just this case but two other criminal cases in Beverly Hills by checking himself into a drug rehabilitation programme, a very unusual disposition in a case that alleged violence.
"Sadly, Mr Furlong rejected all proposals to get into drug rehabilitation, and the Court ultimately decided that it was forced to sentence to him a hefty amount of jail time. We are hopeful that Mr Furlong uses this experience, unpleasant as it may be, to revisit the issue of rehab when he is released."
A judge presiding in the case has required Furlong to serve his full sentence, although there is an outside chance that he could be released in May.
Furlong has famously battled alcohol addiction through his career, having spent time in rehab.