For an excellent treatment of the subject read Herbert Weiner's "Nine and
a half mystics the Kabbala Today ", Chapter one which deals with his
conversation with the last Nazir in Jerusalem, Rav Dovid Cohen zt"l(the
main student in Kabbala of Rav Kook zt"l) entiled "He who touches is
touched". The book "Faith and Folly" by the Chacham Yakov Hillel( a
contemporary expert in Kabbala) is published by Feldheim and discusses
many Halachic issues on the subject. Many of the works by Rabbi Aryeh
Kaplan zt"l draw from and shed light on the subject.