The Judge has the power to sentence someone who violated probation within the sentencing guidelines of that particular state, and depending on the nature of the violation. Under Michigan Law, a Judge has the authority to impose a sentence of jail or prison if a person violates a condition of their probation. 15 months for a first probation violation for you husband's sister sounds rather harsh. Im willing to bet that at the time of sentencing, the Judge either warned your husband and sister that if they violated probation they would get a lenghty sentence, or your husband's sister has comitted more than just one probation violation. However, knowing that your husband's sister received 15months, I would advise your husband to speak with a criminal defense attorney in your area to represent him at his violation hearing in an effort to avoid a lengthy sentence. Good Luck.