Senate Bill 6231 defines hostile architecture as “elements designed to restrict the use of public spaces by individuals experiencing homelessness.” (A PDF of the original bill can be viewed here.)
In the past, those elements have included fencing, large boulders and gravel. If the elements are erected specifically “to prevent people from sitting or lying at street” level, they would be prohibited.
They’re great for un-doing the bolts used to hold lots of stuff in place. Including rocks.