Friend's parents and rehab

I'm just trying to figure out if what my friend's parents did is legal in the state of Oregon. My friend has been experimenting with drugs for quite some time, and his parents have made him go to drug counselors and do other things to try and stop him from using. He mostly smokes marijuana.

Today they took him on a car ride, without telling him where he was going and eventually told him that they were going to a drug rehab center in a very rural, middle of nowhere area in Oregon. I found this both morally and legally questionable.

Here is ORS 163.225 on second degree kidnapping. Do his parents have legal authority over him at the age of 17? If he went willingly but wasn't aware of his rights, does that change anything?

I want to know if what they're doing is also illegal.

I probably don't have anything here.