diff --git a/Dockerfile b/Dockerfile
index 79daa371..4befce9e 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -12,8 +12,9 @@
 # The Debian version and version name must be in sync
 ARG DEBIAN_VERSION=11
 ARG DEBIAN_VERSION_NAME=bullseye
-ARG RUSTC_VERSION=1.60.0
+ARG RUSTC_VERSION=1.61.0
 ARG NODEJS_VERSION=16
+ARG OPA_VERSION=0.40.0
 
 ## Build stage that builds the static files/frontend ##
 FROM --platform=${BUILDPLATFORM} docker.io/library/node:${NODEJS_VERSION}-${DEBIAN_VERSION_NAME}-slim AS static-files
@@ -26,6 +27,21 @@ RUN npm run build
 # Change the timestamp of built files for better caching
 RUN find public -type f -exec touch -t 197001010000.00 {} +
 
+## Build stage that builds the OPA policies ##
+FROM --platform=${BUILDPLATFORM} docker.io/library/debian:${DEBIAN_VERSION_NAME}-slim AS policy
+
+ARG BUILDOS
+ARG BUILDARCH
+ARG OPA_VERSION
+
+ADD --chmod=755 https://github.com/open-policy-agent/opa/releases/download/v${OPA_VERSION}/opa_${BUILDOS}_${BUILDARCH}_static /usr/local/bin/opa
+
+WORKDIR /policies
+COPY ./policies/ /policies
+RUN opa build -t wasm -e "client_registration/allow" -e "login/allow" -e "register/allow" client_registration.rego login.rego register.rego \
+  && tar xzf bundle.tar.gz /policy.wasm \
+  && rm -f bundle.tar.gz
+
 ## Base image with cargo-chef and the right cross-compilation toolchain ##
 # cargo-chef helps with caching dependencies between builds
 # The image Debian base name (bullseye) must be in sync with the runtime variant (debian11)
@@ -106,9 +122,13 @@ RUN mv target/$(/docker-arch-to-rust-target.sh "${TARGETPLATFORM}")/release/mas-
 ## Runtime stage, debug variant ##
 FROM --platform=${TARGETPLATFORM} gcr.io/distroless/cc-debian${DEBIAN_VERSION}:debug-nonroot AS debug
 COPY --from=builder /usr/local/bin/mas-cli /usr/local/bin/mas-cli
+COPY --chmod=444 --from=policy /policies/policy.wasm /policies/policy.wasm
+WORKDIR /
 ENTRYPOINT ["/mas-cli"]
 
 ## Runtime stage ##
 FROM --platform=${TARGETPLATFORM} gcr.io/distroless/cc-debian${DEBIAN_VERSION}:nonroot
 COPY --from=builder /usr/local/bin/mas-cli /usr/local/bin/mas-cli
+COPY --chmod=444 --from=policy /policies/policy.wasm /policies/policy.wasm
+WORKDIR /
 ENTRYPOINT ["/usr/local/bin/mas-cli"]
diff --git a/policies/register.rego b/policies/register.rego
index c918288e..720fb263 100644
--- a/policies/register.rego
+++ b/policies/register.rego
@@ -3,7 +3,8 @@ package register
 import future.keywords.in
 
 default allow := false
-allow := true {
+
+allow {
 	count(violation) == 0
 }
 
@@ -12,7 +13,7 @@ violation[{"field": "username", "msg": "username too short"}] {
 }
 
 violation[{"field": "username", "msg": "username too long"}] {
-	count(input.user.username) >= 15 
+	count(input.user.username) >= 15
 }
 
 # Allow any domains if the data.allowed_domains array is not set
@@ -37,5 +38,3 @@ violation[{"field": "email", "msg": "email domain not allowed"}] {
 	some banned_domain in data.banned_domains
 	glob.match(banned_domain, ["."], domain)
 }
-
-
diff --git a/policies/register_test.rego b/policies/register_test.rego
index c84a4676..740e22cc 100644
--- a/policies/register_test.rego
+++ b/policies/register_test.rego
@@ -7,26 +7,30 @@ test_allow_all_domains {
 }
 
 test_allowed_domain {
-	allow 
-		with input.user as mock_user
+	allow with input.user as mock_user
 		with data.allowed_domains as ["*.element.io"]
 }
 
 test_not_allowed_domain {
-	not allow 
-		with input.user as mock_user
+	not allow with input.user as mock_user
 		with data.allowed_domains as ["example.com"]
 }
 
 test_banned_domain {
-	not allow 
-		with input.user as mock_user
+	not allow with input.user as mock_user
 		with data.banned_domains as ["*.element.io"]
 }
 
 test_banned_subdomain {
-	not allow 
-		with input.user as mock_user
+	not allow with input.user as mock_user
 		with data.allowed_domains as ["*.element.io"]
 		with data.banned_domains as ["staging.element.io"]
 }
+
+test_short_username {
+	not allow with input.user as {"username": "a", "email": "hello@element.io"}
+}
+
+test_long_username {
+	not allow with input.user as {"username": "aaaaaaaaaaaaaaaaaaaaaaaaaaaaa", "email": "hello@element.io"}
+}