Anyone can provide the services of a novelty/patentablity search or patent landscape report. However, a freedom to operate analysis is a different story. Even as a registered patent agent I am leery of freedom to operate.
It is clear that only an attorney (does not need to be registered patent attorney) can provide a freedom to operate opinion. That is an analysis of the likelihood of being sued for infringement and the likelihood of prevailing if sued. An attorney can't have liability waived by a client for professional errors therefore they are expensive.
Although a non-attorney might generate an analysis rather than an opinion, I think it is too fine a line and a client would take an analysis as an opinion. Of course search firms do freedom to operate searches (possibly with some analysis) for attorneys and the attorneys use that as the basis for an opinion.
A search company can limit its liability contractually - an attorney or agent can't in most locations.
In a novelty search it is pretty standard to have a disclaimer that no search by anyone is guaranteed to find everything. I heard a litigator give a talk to searchers and patent prosecutors. He said whatever combined time and effort is spent searching as part of a patent prosecution by the applicant and examiner, if the resulting patent is asserted, the time and effort spent to find prior art by the defense will be at least 10X.