How can you make someone go to rehab? ?

You can't make someone do anything they do not wish to do. And if someone is forced into rehab (by a doctor, for example), and they don't want to be there, then the first thing most people will do when they get out is to start using again.

Rehab isn't magical.

You can talk to a therapist about an intervention. This may help or not.

An addict has to have the DESIRE to change and the WILL to become sober. It's not something you can give to them

You can't. Only the addict can cure themselves. Even after all these years, I still sometimes think about it (just one more time won't hurt). But it does. That's why I never went back. And those Psy.s, self help groups, religious persecutors, mental health institutions et. al, are a bunch of crap.

A court order can force them, but if it isn't something that they want to do, they will just go back to their addiction.