diff --git a/internal/vowifi/carrier_ipcc.go b/internal/vowifi/carrier_ipcc.go
index e84e181..a84c026 100644
--- a/internal/vowifi/carrier_ipcc.go
+++ b/internal/vowifi/carrier_ipcc.go
@@ -661,6 +661,12 @@ func inspectIgnoredCarrierFields(plists []ipccPlist, warnings *ipccWarningSet) {
 				warnings.add("apn_settings_ignored", "APN settings and credentials are outside the VoCat carrier-profile importer", fullPath)
 			case key == "media" && strings.Contains(strings.ToLower(strings.Join(keyPath, ".")), "imsconfig"):
 				warnings.add("device_media_overrides_ignored", "device-family media and codec overrides require hardware validation and were not imported", fullPath)
+			case key == "countryoforiginationformat":
+				warnings.add(
+					"country_of_origination_format_not_imported",
+					"CountryOfOriginationFormat was not imported because VoCat has no trusted runtime country source; a P-Access-Network-Info value must not be fabricated",
+					fullPath,
+				)
 			case strings.Contains(key, "emergency") || strings.Contains(key, "e911"):
 				warnings.add("emergency_settings_ignored", "emergency-service settings are never imported", fullPath)
 			}
diff --git a/internal/vowifi/carrier_ipcc_test.go b/internal/vowifi/carrier_ipcc_test.go
index 67b1a9e..a9a4a9e 100644
--- a/internal/vowifi/carrier_ipcc_test.go
+++ b/internal/vowifi/carrier_ipcc_test.go
@@ -42,9 +42,12 @@ func TestImportCarrierIPCCConvertsBinaryAndXMLPlistsSafely(t *testing.T) {
 				},
 				"IMSConfig": map[string]any{
 					"EnableWiFiCallingWithoutEntitlement": true,
-					"Signaling":                           map[string]any{"UseIPSec": true},
-					"Media":                               map[string]any{"SupportPCMA": false},
-					"Emergency":                           map[string]any{"E911OverITechSupported": true},
+					"Signaling": map[string]any{
+						"UseIPSec":                   true,
+						"CountryOfOriginationFormat": "PANI",
+					},
+					"Media":     map[string]any{"SupportPCMA": false},
+					"Emergency": map[string]any{"E911OverITechSupported": true},
 				},
 			},
 		},
@@ -79,6 +82,7 @@ func TestImportCarrierIPCCConvertsBinaryAndXMLPlistsSafely(t *testing.T) {
 		"entitlement_bypass_ignored",
 		"apn_settings_ignored",
 		"device_media_overrides_ignored",
+		"country_of_origination_format_not_imported",
 		"emergency_settings_ignored",
 	} {
 		if !hasIPCCWarning(result.Warnings, code) {
diff --git a/internal/vowifi/ims/provider.go b/internal/vowifi/ims/provider.go
index c68fc90..1237c44 100644
--- a/internal/vowifi/ims/provider.go
+++ b/internal/vowifi/ims/provider.go
@@ -991,19 +991,17 @@ func (session *Session) buildRegister(
 	}
 	lines = append(lines, "User-Agent: "+userAgent)
 
-	defaultPANI := "IEEE-802.11;i-wlan-node-id=000000000000;network-provided"
-	pani := defaultPANI
-	if registerOptions.PAccessNetworkInfo != nil {
-		pani = *registerOptions.PAccessNetworkInfo
-	}
-
 	if registerOptions.PPreferredIdentity {
 		lines = append(lines, "P-Preferred-Identity: <"+session.identity.public+">")
 	}
 	if value := strings.TrimSpace(registerOptions.PVisitedNetworkID); value != "" {
 		lines = append(lines, `P-Visited-Network-ID: "`+value+`"`)
 	}
-	if pani != "" {
+	// PANI carries access/location information and must not be fabricated.
+	// In particular, "network-provided" identifies a value inserted by a
+	// trusted network proxy, not one generated by this UE.  Send the header
+	// only when a carrier profile explicitly supplies a reviewed value.
+	if pani := optionalRegisterHeader(registerOptions.PAccessNetworkInfo); pani != "" {
 		lines = append(lines, "P-Access-Network-Info: "+pani)
 	}
 	if value := strings.TrimSpace(registerOptions.CellularNetworkInfo); value != "" {
@@ -1047,6 +1045,13 @@ func (session *Session) buildRegister(
 	return []byte(strings.Join(lines, "\r\n")), nil
 }
 
+func optionalRegisterHeader(value *string) string {
+	if value == nil {
+		return ""
+	}
+	return strings.TrimSpace(*value)
+}
+
 func (session *Session) buildContact(contactAddress string, registerOptions vowifi.IMSRegisterOptions) string {
 	base := fmt.Sprintf("<sip:%s@%s;transport=%s>", session.identity.user, contactAddress, session.transport)
 	instanceID := session.instanceID
diff --git a/internal/vowifi/ims/provider_test.go b/internal/vowifi/ims/provider_test.go
index 25d4341..4792dff 100644
--- a/internal/vowifi/ims/provider_test.go
+++ b/internal/vowifi/ims/provider_test.go
@@ -377,6 +377,7 @@ func serveRegistration(listener *net.UDPConn, nonce string, confirmSMS bool) err
 		for _, forbidden := range []string{
 			"p-visited-network-id",
 			"p-preferred-identity",
+			"p-access-network-info",
 		} {
 			if headers[forbidden] != "" {
 				return fmt.Errorf(
@@ -386,9 +387,6 @@ func serveRegistration(listener *net.UDPConn, nonce string, confirmSMS bool) err
 				)
 			}
 		}
-		if headers["p-access-network-info"] != "IEEE-802.11;i-wlan-node-id=000000000000;network-provided" {
-			return fmt.Errorf("REGISTER P-Access-Network-Info = %q", headers["p-access-network-info"])
-		}
 		if !strings.Contains(headers["allow"], "MESSAGE") ||
 			!strings.Contains(string(packet[:count]), "Accept-Contact: *;+g.3gpp.smsip") {
 			return fmt.Errorf("REGISTER omitted SMS-over-IMS capability: Allow=%q", headers["allow"])
@@ -497,6 +495,26 @@ func serveRegistration(listener *net.UDPConn, nonce string, confirmSMS bool) err
 	return nil
 }
 
+func TestOptionalRegisterHeaderRequiresExplicitNonemptyValue(t *testing.T) {
+	explicit := "  IEEE-802.11;i-wlan-node-id=aabbccddeeff  "
+	empty := "  "
+	for _, test := range []struct {
+		name  string
+		value *string
+		want  string
+	}{
+		{name: "unspecified", value: nil, want: ""},
+		{name: "explicit omission", value: &empty, want: ""},
+		{name: "explicit value", value: &explicit, want: "IEEE-802.11;i-wlan-node-id=aabbccddeeff"},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			if got := optionalRegisterHeader(test.value); got != test.want {
+				t.Fatalf("optionalRegisterHeader() = %q, want %q", got, test.want)
+			}
+		})
+	}
+}
+
 func serveRefreshFailure(listener *net.UDPConn, nonce string) error {
 	var callID string
 	for step := 0; step < 3; step++ {