LSASS is a System level process, so any kind of access to it will require Admin level privileges.  I would guess that your user had admin access and you didn't realize it.  You can [check your level of access through a batch script][1] to confirm.  If you still have access to the machine you RDP'ed in to.

To the best of my knowledge LSASS has always been a protected process.  It's needed for user login to for distributing access tokens so it definitely wouldn't be a user level process.   


  [1]: https://stackoverflow.com/questions/4051883/batch-script-how-to-check-for-admin-rights