The SIN databases are matters of public record, IIRC. They have to be, or otherwise anyone can claim to be a citizen of X corp or Y nation. However, note that merely being able to search the SIN databases doesn't mean that there will be actionable or legitimate information there. In addition to having 'classified' or 'redacted' entries, you can also have entries that are 'misfiled', making them harder to find. So if Horizon wants to keep some of the info on Gary Cline's SIN under wraps, there are plenty of ways to do it. That's just an example, mind you, but the truth is that it makes sense for the basic info on the SIN registries to be searchable by all law enforcement and corporate security types. Of course, your KE cop in Seattle probably won't be able to search the SIN database for all Renraku employees at the home office in Chiba, but Renraku Citizens in Seattle and the surrounding area? Most likely. Though of course if the two corps are having a spat, the requests can take time for 'processing' due to 'increased demand', or might get 'lost in transmission' or 'corrupted accidentally'. You know the drill.