Like right to bear arms?

Restricting gun availability is a proactive step against terrorism reduces freedoms that is controversial.

I see that I was not being clear, my apologies. What I meant was that retaining the right to bear arms is a proactive step against terrorism (by minimizing "soft" civilian targets) that a)preserves freedoms, and b)is nonetheless controversial.

The parent comment was making the argument that there are no freedom-preserving counter terrorism measures that are controversial. The right to bear arms is a counter example.

In that case it's unclear that it is a proactive step against terrorism (for the reason I said, domestic terrorists get guns more easily) which is a different kind of debate than cases where everyone agrees a freedom limiting step would prevent terrorism and the question is if it's worth it.