diff --git a/subsys/bluetooth/controller/hci/hci.c b/subsys/bluetooth/controller/hci/hci.c
index f7b4428cd4a..9178879ad03 100644
--- a/subsys/bluetooth/controller/hci/hci.c
+++ b/subsys/bluetooth/controller/hci/hci.c
@@ -570,7 +570,12 @@ static void le_read_supp_states(struct net_buf *buf, struct net_buf **evt)
 	rp = cmd_complete(evt, sizeof(*rp));
 	rp->status = 0x00;
 
-	sys_put_le64(0x000003ffffffffff, rp->le_states);
+	/* All states and combinations supported except:
+	 * Initiating State + Passive Scanning
+	 * Initiating State + Active Scanning
+	 */
+	/*@todo: conditionally disable states based on Kconfig variables */
+	sys_put_le64(0x000003ffff3fffff, rp->le_states);
 }
 
 #if defined(CONFIG_BLUETOOTH_BROADCASTER)
diff --git a/subsys/bluetooth/controller/ll_sw/ctrl.c b/subsys/bluetooth/controller/ll_sw/ctrl.c
index 02e93960959..a055a5a6738 100644
--- a/subsys/bluetooth/controller/ll_sw/ctrl.c
+++ b/subsys/bluetooth/controller/ll_sw/ctrl.c
@@ -8142,7 +8142,7 @@ u32_t radio_adv_enable(u16_t interval, u8_t chl_map, u8_t filter_policy)
 	u32_t ret;
 
 	if (_radio.advertiser.is_enabled) {
-		return 1;
+		return BT_HCI_ERR_CMD_DISALLOWED;
 	}
 
 	pdu_adv = (struct pdu_adv *)
@@ -8153,19 +8153,19 @@ u32_t radio_adv_enable(u16_t interval, u8_t chl_map, u8_t filter_policy)
 		void *link;
 
 		if (_radio.advertiser.conn) {
-			return 1;
+			return BT_HCI_ERR_CMD_DISALLOWED;
 		}
 
 		link = mem_acquire(&_radio.link_rx_free);
 		if (!link) {
-			return 1;
+			return BT_HCI_ERR_MEM_CAPACITY_EXCEEDED;
 		}
 
 		conn = mem_acquire(&_radio.conn_free);
 		if (!conn) {
 			mem_release(link, &_radio.link_rx_free);
 
-			return 1;
+			return BT_HCI_ERR_MEM_CAPACITY_EXCEEDED;
 		}
 
 		conn->handle = 0xFFFF;
@@ -8347,7 +8347,7 @@ failure_cleanup:
 		mem_release(conn, &_radio.conn_free);
 	}
 
-	return 1;
+	return BT_HCI_ERR_CMD_DISALLOWED;
 }
 
 u32_t radio_adv_disable(void)
@@ -8375,7 +8375,7 @@ u32_t radio_adv_disable(void)
 		}
 	}
 
-	return status;
+	return status ? BT_HCI_ERR_CMD_DISALLOWED : 0;
 }
 
 u32_t radio_adv_is_enabled(void)
@@ -8408,7 +8408,7 @@ u32_t radio_scan_enable(u8_t type, u8_t init_addr_type, u8_t *init_addr,
 	u32_t ret;
 
 	if (_radio.scanner.is_enabled) {
-		return 1;
+		return BT_HCI_ERR_CMD_DISALLOWED;
 	}
 
 	_radio.scanner.type = type;
@@ -8479,7 +8479,7 @@ u32_t radio_scan_enable(u8_t type, u8_t init_addr_type, u8_t *init_addr,
 	}
 
 	if (ret_cb != TICKER_STATUS_SUCCESS) {
-		return 1;
+		return BT_HCI_ERR_CMD_DISALLOWED;
 	}
 
 	_radio.scanner.is_enabled = 1;
@@ -8517,7 +8517,7 @@ u32_t radio_scan_disable(void)
 		}
 	}
 
-	return status;
+	return status ? BT_HCI_ERR_CMD_DISALLOWED : 0;
 }
 
 u32_t radio_scan_is_enabled(void)
@@ -8548,23 +8548,20 @@ u32_t radio_connect_enable(u8_t adv_addr_type, u8_t *adv_addr, u16_t interval,
 	void *link;
 
 	if (_radio.scanner.conn) {
-		return 1;
+		return BT_HCI_ERR_CMD_DISALLOWED;
 	}
 
 	link = mem_acquire(&_radio.link_rx_free);
 	if (!link) {
-		return 1;
+		return BT_HCI_ERR_MEM_CAPACITY_EXCEEDED;
 	}
 
 	conn = mem_acquire(&_radio.conn_free);
 	if (!conn) {
 		mem_release(link, &_radio.link_rx_free);
-
-		return 1;
+		return BT_HCI_ERR_MEM_CAPACITY_EXCEEDED;
 	}
 
-	radio_scan_disable();
-
 	_radio.scanner.adv_addr_type = adv_addr_type;
 	memcpy(&_radio.scanner.adv_addr[0], adv_addr, BDADDR_SIZE);
 	_radio.scanner.conn_interval = interval;
@@ -8684,7 +8681,7 @@ u32_t ll_connect_disable(void)
 	u32_t status;
 
 	if (_radio.scanner.conn == 0) {
-		return 1;
+		return BT_HCI_ERR_CMD_DISALLOWED;
 	}
 
 	status = radio_scan_disable();
diff --git a/subsys/bluetooth/controller/ll_sw/ll_adv.c b/subsys/bluetooth/controller/ll_sw/ll_adv.c
index 754ba24fd0e..b27e3d13cc7 100644
--- a/subsys/bluetooth/controller/ll_sw/ll_adv.c
+++ b/subsys/bluetooth/controller/ll_sw/ll_adv.c
@@ -58,7 +58,7 @@ u32_t ll_adv_params_set(u16_t interval, u8_t adv_type,
 	struct pdu_adv *pdu;
 
 	if (radio_adv_is_enabled()) {
-		return 0x0C; /* Command Disallowed */
+		return BT_HCI_ERR_CMD_DISALLOWED;
 	}
 
 #if defined(CONFIG_BLUETOOTH_CONTROLLER_ADV_EXT)
@@ -341,9 +341,9 @@ u32_t ll_adv_enable(u8_t enable)
 	u32_t status;
 
 	if (!enable) {
-		status = radio_adv_disable();
-
-		return status;
+		return radio_adv_disable();
+	} else if (radio_adv_is_enabled()) {
+		return 0;
 	}
 
 	/* TODO: move the addr remembered into controller
diff --git a/subsys/bluetooth/controller/ll_sw/ll_master.c b/subsys/bluetooth/controller/ll_sw/ll_master.c
index f0794232435..76328bc76a1 100644
--- a/subsys/bluetooth/controller/ll_sw/ll_master.c
+++ b/subsys/bluetooth/controller/ll_sw/ll_master.c
@@ -22,6 +22,10 @@ u32_t ll_create_connection(u16_t scan_interval, u16_t scan_window,
 {
 	u32_t status;
 
+	if (radio_scan_is_enabled()) {
+		return BT_HCI_ERR_CMD_DISALLOWED;
+	}
+
 	status = radio_connect_enable(peer_addr_type, peer_addr, interval,
 				      latency, timeout);
 
diff --git a/subsys/bluetooth/controller/ll_sw/ll_scan.c b/subsys/bluetooth/controller/ll_sw/ll_scan.c
index 5d6a197efef..544069bdbe4 100644
--- a/subsys/bluetooth/controller/ll_sw/ll_scan.c
+++ b/subsys/bluetooth/controller/ll_sw/ll_scan.c
@@ -32,7 +32,7 @@ u32_t ll_scan_params_set(u8_t type, u16_t interval, u16_t window,
 			 u8_t own_addr_type, u8_t filter_policy)
 {
 	if (radio_scan_is_enabled()) {
-		return 0x0C; /* Command Disallowed */
+		return BT_HCI_ERR_CMD_DISALLOWED;
 	}
 
 	/* type value:
@@ -61,9 +61,10 @@ u32_t ll_scan_enable(u8_t enable)
 	u32_t status;
 
 	if (!enable) {
-		status = radio_scan_disable();
-
-		return status;
+		return radio_scan_disable();
+	} else if (radio_scan_is_enabled()) {
+		/* Duplicate filtering is processed in the HCI layer */
+		return 0;
 	}
 
 	status = radio_scan_enable(ll_scan.type, ll_scan.tx_addr,