Halakhah in the Dead Sea Scrolls?
Somewhat similar, perhaps, is the question of using "midrash" for the scriptural exegesis in the Qumran biblical commentaries. The word is an anachronism, but rabbinic midrash does share some of the assumptions and techniques of the Scrolls. In this case I would avoid using "midrash" for the Scrolls, because they give us their own word, pesher, for their commentary technique.
That said, I do tend to refer to halakhah in the Scrolls (see, e.g., the bibliography for 4QMMT). I am by no means alone in this. The ambivalence about the term among Qumranologists is reflected in the Encyclopedia of the Dead Sea Scrolls, where if you look up "Halakhic Works" (p. 328) you will be referred to the article on "Legal Works" (pp. 479-80) in which Larry Schiffman refers to one of the texts as "Halakhah A," following Joseph Baumgarten. Schiffman also applies the term halakhah to 4QMMT in his article on the same (pp. 558-60) and Yaakov Elman has a section on "The Qumran Halakhah" in his "Mishnah and Tosefta" article (pp. 569-74). Schiffman also defends this terminology in his article "The Dead Sea Scrolls and Rabbinic Halakhah" in The Dead Sea Scrolls as Background to Postbiblical Judaism and Early Christianity (ed. Davila), 3-24, esp. p. 5.
It would be nice if we had a good word that applied to the Qumran legal traditions alone, but until then I think a lot of people will continue to say halahkah. As long as we make clear what we mean by it, I don't think this is harmful.
This Wikipedia article on halakhah looks pretty good, although one always has to be cautious with Wikipedia.