Do the FAA's InFO publications carry any regulatory or legal weight?
An InFO (Information For Operators) document is an informational document containing recommendations. Quoting directly from FAA Order 8000.91:


  Much like a Safety Alert for Operators (SAFO), which contains critical safety information, an Information for Operators (INFO) message contains valuable information for operators that should help them meet administrative requirements or certain regulatory requirements with relatively low urgency or impact in safety. INFOs contain information or a combination of information and recommended action to be taken by the respective operators identified in each individual INFO.


They are not regulatory changes/obligations (like ADs) or formal notices of violation (administrative actions) - they're just a "friendly hint" that the FAA is concerned about something and would like operators to be aware of it and take action if the operator's analysis determines it to be necessary.
If the situation addressed in an InFO or SAFO document doesn't improve it may wind up prompting a regulatory change.

The InFO and SAFO programs are very similar, so FAA Order 8000.87A covering the SAFO program may also be of interest.