I don't believe the executive branch rescue of Terri would be extralegal in any respect. The executive branch has a DUTY to uphold the Constitutional RIGHTS of it's citizens. Thus, the EXECUTIVE BRANCH has a duty in this EXTRAORDINARY circumstance of life and death and CRUEL and UNUSUAL punishment suffered by Terri to protect her rights, (and those of her family), by removing Terri from the clutches of those who would deny them.
Acting exceptionally in this exceptional situation would not harm the RULE of LAW even a little. ALLOWING the INJUSTICE FORCED upon Terri to STAND will establish HORRIBLE precedent, the consequences of which we cannot begin to fathom.
According to Judge Roy Moore, the Rule of Law is the Constitution itself.
Therefore, according to the Rule of Law, Jeb Bush is empowered to rescue Terri by Article 1, Section 2, of the Florida State Constitution.
Others have also agreed that the Constitution gives this power to the Governor, such as Dr. Alan Keyes, and the Thomas More Law Center.
As far as principles go, life trumps them all, because the law has the promotion of life as its purpose and end.