There are certain types of checks--e.g. contacting the credit rating agencies to run a credit report--for which they need your consent. But anything readily publically avaliable (e.g. through a web or internet search), they could obviously view whenever they wanted. Similarly, there are some businesses which agregate information which is publically available (e.g. criminal convictions, evictions, etc.) but can be difficult or time consuming to get; however, as long as that is information which any member of the public could get, if he or she were motivated enough, it again is something the prospective employer could obtain in advance of the interview. So the answer is, it may well be the case that they only obtained information which it is legal for them to get.