This was not a "welfare check"... this was an "open structure" call. However, for conversation sake, if this was a welfare call, can you explain how this Woman's 4th amendment right would have been violated by a cop knocking at her door? "Knock and Talk's" are perfectly legal, even if they are not responding to a call. That doesn't mean you have to let them in your house. Knock and Talk Law and Legal Definition | USLegal, Inc.