I guess technically Christian supposing they affirm the Trinity, though keeping the Law de facto denies the saving work of Christ's Crucifixion and Resurrection.
Not to hijack the thread, but I have recently become fascinated with how different people define "Christian." Even more academically-minded or "neutral" definitions might call Mormonism or Jehovah's Witnesses or whatever a "different religion," and yet they'd have no problem labeling the early followers of Arius as "Arian
Christians" and describing the Germanic tribes that came to adopt the teachings of Arius as "converting to
Christianity."
It has really led me to believe that any definition of "Christian" should probably include groups that are heretical ... otherwise, you cannot be a heretical Christian. Nobody calls a Buddhist a "heretic," because he is simply just of another religion. "Heretic" should be reserved for someone who is in some sense Christian but rejects a fundamentally essential teaching of (lower case) orthodox Christianity. In other words, while I definitely think anyone who rejects the Trinity is a heretic, I'm not sure it's the best cutoff for being a Christian. If I were doing an academic study, I would probably place the cutoff at some vague definition of affirming the Resurrection and being a "follower of Jesus." So, Messianic Jews would definitely count for me, as would Oneness Pentecostals, Unitarians and even Mormons (though all three should be labeled as heretical and fringe).