Firewall – prevent openvpn client from changing ip of tap device

I have an openvpn server behind a firewall, clients are assigned static IP addresses with specific ifconfig-push directives in the client-config-dir. The problem is that clients can change their assigned IP's (e.g: ifconfig tap0 a.b.c.d up) making all my firewall rules useless… is there a way to prevent them from changing their IP?

server.conf:

mode server
tls-server

local 10.0.0.150
port 1194
proto udp

#bridging directive
dev tap0 ## If you need multiple tap devices, add them here
up "/etc/openvpn/up.sh br0 tap0 1500"
down "/etc/openvpn/down.sh br0 tap0"

persist-key
persist-tun

#certificates and encryption
ca /etc/openvpn/easy-rsa/keys/ca.crt
cert /etc/openvpn/easy-rsa/keys/server.crt
key /etc/openvpn/easy-rsa/keys/server.key  # This file should be kept secret
dh /etc/openvpn/easy-rsa/keys/dh2048.pem
tls-auth /etc/openvpn/easy-rsa/keys/ta.key 0 # This file is secret

#DHCP Information
ifconfig-pool-persist ipp.txt
server-bridge 10.0.0.150 255.255.255.0 10.0.0.151 10.0.0.170
client-config-dir /etc/openvpn/client-config

#log and security
user nobody
group nogroup
keepalive 60 240
status openvpn-status.log
verb 3

client-config/some_client:

ifconfig-push 10.0.0.1 255.255.255.0