As is noted above, it appears likely that a decision may be challenged on proportionality grounds if it constitutes a significant interference with an important or fundamental right. The Court have not defined an ‘important’ right. In the Pham case, it was considered that a decision to withdraw a suspected terrorist’s British nationality interfered with a sufficiently important right to allow the Supreme Court to consider the decision’s proportionality.
Gage v Scottish Ministers  CSOH 174 was one of the first cases to consider proportionality post-Pham. In this case, a decision to detain a prisoner in a prison where he was subjected to second-hand smoke was considered not to interfere with a sufficiently important right so as to enable the decision to be challenged on proportionality grounds. As a result, the challenge was considered under reasonableness/rationality grounds instead.