Statutory guidelines = the actual penalty provisions under the offence in the Crimes Act etc., as well as the mandatory considerations with respect to mitigating and aggravating factors in sentencing under the Sentencing and Procedure Act or whatever it is.
Judicial guidelines = precedent from case law as to the application of sentencing principles, any court rules and the bench books are a good resource.
Mandatory sentencing is a talking point because it's arguably legislative interference contrary to the separation of powers and the judiciary's exclusive function of adjudicating and punishing criminal guilt. It curtails judicial discretion which is the manner in which judges use to mould punishments to the circumstances of the offence and the those of the offender and in that way is arguably both an intrusion upon the judiciary and removing one of the legal system's means of actually administering 'just' outcomes.