Well, Paxton was played by a 50 something Peter Weller and Taggart's syndrome is supposed to be fatal by age 20, so Paxton must've been being treated for 30 years. If it were illegal, how would T'Pol know it's an accepted treatment for the disease by humans? Most people wouldn't take it and they'd all die of it. T'Pol, one of the founders of the Federation, is obviously advocating its continued use saying: "The very thing you're warning humans to avoid is what's keeping you alive. Alien knowledge, freely shared. You're not only a terrorist, you're a hypocrite."