There is no function for unprotecting symbols.
i1 : mutable symbol s o1 = true
i2 : s = 5 o2 = 5
i3 : s o3 = 5
i4 : protect symbol s o4 = s o4 : Symbol
i5 : mutable symbol s o5 = false
i6 : try s = 7
i7 : s o7 = 5