MB 38: One who is banned and one who has Tsara'as* - See in the Lechem Chamudos (commentary to the Rosh by R. Yom Tov Lipman Heller, early 17th cent.) and the Shach (Sifsey Kohen, commentary to the Shulchan Aruch, by R. Shabsay Ben Meir HaKohen, mid-17th cent.) in Yoreh Deah (one of the four main sections of the Shulchan Aruch) Siman 334, Paragraph 2 and in other later authorities, who rule the opposite (i.e., that such people are required to put on Tefilin); the Pri Megadim (R. Yosef Teomim, mid-18th cent.) writes that such people should put on Tefilin without a blessing [since there is doubt about their obligation to put on Tefilin, and we avoid a possible blessing made in vain - LC], but from the Biur HaGra (commentary on the Shulchan Aruch by R. Eliyahu of Vilna - The Vilna Gaon, late 18th cent.) apparently it is apparent that they are also required to make a blessing.
[*Tsara'as, a skin disease described in Leviticus, Chap. 13, is commonly translated as "leprosy," but is not equivalent to the skin disease seen today of the same name. Our Sages say that Tsara'as came to a person as a punishment for speaking Loshon HaRa (forbidden speech denigrating someone), and the person was physically and spiritually isolated from society until he/she was pronounced clear of the disease. This may be the common link between Tsara'as and one who is banned (for some serious transgression deemed threatening to the community), since the latter is spiritually isolated from the community. In any case, I had thought that Tsara'as as described in the Torah is no longer used by G-d as a punishment, and if so it's curious that the Shulchan Aruch mentions it, since in general it deals only with laws pertaining to post-Temple times. LC]
N.B. The next section deals with qualifications of those who may write the Torah passages for Tefilin and from whom they may be purchased. It gets quite technical, and I have attempted to shorten the Mishna Bruras in some places, as requested by Rabbi Menken, our editor in such situations.