is this a voilation if the disclosures were not sent to the co-borrower by mail?...where I can find the regulatory requirements for this.
The regulatory requirements that matter most are the specific sections of Regs. B & Z, RESPA, flood, and any other applicable reg that require you to deliver one or more disclosures "in writing." That's where you are exposed to penalties. ESIGN is part of the total picture, but it has no penalties.