the only thing the draft can force you to do legally is sign up, and go the place they tell you to go for your physical and take it. the 14th amendment makes involuntary servitude unconstitutional. they can't force you to join the military.  when you get off the bus at the induction center, if you get that far. they will make a statement like, or similar to, "anybody who is here to join the us army, walk into that building." if you walk in, you just volunteered. they don't tell you that, they let you believe you have no choice, if that's what you believe, and most do. if you don't want to volunteer, don't do what they told you. they'll yell at you, threaten you, maybe even assault you or threaten to do it. it might last for hours, as you get threatened by entire teams of officers. hold out, and do not agree to go in the building, or step over the yellow line, or whatever it is they told you to do. eventually they'll give up and send you home. they can't make you join. they can't drag or carry you into the building. you have to volunteer, even though they don't tell you that's what you'll be doing if you do what they tell you.  don't worry, be tough, don't be afraid, don't give in. they'll let you go.
Canada