// the policy lookup would ambiguous.
	if r.TLS == nil {
		writeSTSErrorResponse(ctx, w, ErrSTSInsecureConnection, errors.New("No TLS connection attempt"))
		return
	}

	// A client may send a certificate chain such that we end up
	// with multiple peer certificates. However, we can only accept
	// a single client certificate. Otherwise, the certificate to
	// policy mapping would be ambiguous.