se·cede 
(sĭ-sēd)
(sĭ-sēd)intr.v. se·ced·ed, se·ced·ing, se·cedes
To withdraw formally from membership in a state, union, or other political entity.
[Latin sēcēdere, to withdraw : sē-, apart; see s(w)e- in the Appendix of Indo-European roots + cēdere, to go; see ked- in the Appendix of Indo-European roots.]