no they couldn't. They could not bring about her death by removing the feeding tube without her permission and since she didn't sign a living will, her HINO had to convince a judge that she expressed a desire not be kept alive by artificial means. BUT, the feeding tube was not considered extraordinary means back then...it was considered part of normal care so they passed that law so they could kill her.
To my earlier point, if Michael alwasy knew Terri wouldn't want to live like this, then why did he put the tube in in the first place??? He is not being consistant.