By all means, charge any American supporting ISIS with treason. Treason is clearly defined in the Constitution. However, the Constitution PROHIBITS the revocation of citizenship! Citizenship can ONLY be renounced by the individuals in question. We know who these traitors are, so why not arrest them upon reentry to the US?
I’ve voted for Cruz and support him on most issues, but he is dead wrong on this one. The Constitution prohibits stripping of citizenship for good reason!