Erectile dysfunction is not uncommon after radical prostatectomy and men who undergo ADT in addition to this are likely to show further decline in their ability to engage in penetrative intercourse, as well as their desire to do so.  A study looking at the differences of using GnRH-A (and androgen suppressant) or an orchiectomy report differences in sexual interest, the experience of erections, and the prevalence of participating in sexual activity. Men reporting no sexual interest increased from % to % after orchiectomy, and from % to % after GnRH-A; men who experienced no erections increased from % to %; and men who did not report engaging in sexual activity increased from % to % after orchiectomy and % to %.  This study suggests that the GnRH-A and orchiectomy had similar effects on sexual functioning. A vicious cycle whereby lowering testosterone levels leads to decreased sexual activity, which in turn cause both free and total testosterone levels to decline even further.  This demonstrates the importance of androgens for maintaining sexual structures and functions.  
This is a gray area. Testosterone is a schedule III drug and is illegal to obtain without a prescription. The compounding pharmacies and male HRT clinics (also many anti-aging clinics) often have a doctor in-house that will interpret your test results and have a phone consultation with you. That doctor, who you never see in person, will prescribe your testosterone (as well as growth hormone, which is an even grayer area) and any other ancillary drugs ( such as Nolvadex or Arimidex to prevent side effects like gynecomastia ). They usually don’t accept insurance and will ship your HRT drugs out by mail within one week. SO… technically, you’re getting your drugs from a legal pharmacy, which also happens to have a doctor on staff to provide the prescription. I don’t think you’d have anything to worry about in court. The HRT or Anti-Aging clinic, on the other hand, might have some legal questions to answer should the DA or DEA ever decide to pay them a visit, which has happened in the past.