Should it be illegal to help a terminally-ill person die?

I agree!

It IS illegal.

Assisted suicide is legal in the three American states of Oregon (via the Oregon Death with Dignity Act),[34] Washington (by Washington Death with Dignity Act), and Montana (through the 2009 trial court ruling Baxter v. Montana). There are relatively substantial barriers to the use of some of these provisions.

For instance, Oregon requires a physician to prescribe medication but it must be self-administered. The prognosis must be for a life span of 6 months or less. The person must be a resident of Oregon. A written request for prescription and two oral requests from the patient are also needed to escape criminal liability, plus written confirmation by doctor that the act is voluntary and informed. This limited model has withstood constitutional scrutiny: Gonzales v Oregon 368 F. 3d 1118 (2004),[35] affirmed by 546 U.S. 243 (2006)

I stand corrected. I don't live in any of the 3 states. I like the fact that it puts the decision and administration ultimately on the patient and not the doctor. And, only the patient can make the decision.