diff --git a/server/migrations/004_unique_users_members.sql b/server/migrations/004_unique_users_members.sql
new file mode 100644
index 0000000..9db96ac
--- /dev/null
+++ b/server/migrations/004_unique_users_members.sql
@@ -0,0 +1,2 @@
+ALTER TABLE users_members
+    ADD UNIQUE (user_id, member_id);
diff --git a/server/src/auth.rs b/server/src/auth.rs
index 78362e7..4295958 100644
--- a/server/src/auth.rs
+++ b/server/src/auth.rs
@@ -12,8 +12,8 @@ use sqlx::PgPool;
 use tokio::task;
 
 use crate::{
-    database::model::{Session, UserMember},
-    model::{member::Roles, User},
+    database::model::Session,
+    model::User,
 };
 
 mod error;
diff --git a/server/src/routes.rs b/server/src/routes.rs
index 6f0f452..d382eea 100644
--- a/server/src/routes.rs
+++ b/server/src/routes.rs
@@ -8,7 +8,6 @@ pub mod user;
 pub fn routes() -> Router<AppState> {
     Router::new()
         .route("/", get(root))
-        // .route("/member/:id", get())
         .merge(member::routes())
         .merge(auth::routes())
         .merge(user::routes())
diff --git a/server/src/routes/user.rs b/server/src/routes/user.rs
index 5cb7ceb..a1b0d32 100644
--- a/server/src/routes/user.rs
+++ b/server/src/routes/user.rs
@@ -7,7 +7,9 @@ use axum::{
 
 use crate::{
     auth::get_user_from_header,
-    model::{member::Roles, User},
+    database::model::{Member as DbMember, UserMember as DbUserMember},
+    model::{member::Roles, Member, User},
+    util::convert_vec,
     AppState,
 };
 
@@ -29,10 +31,24 @@ pub async fn members_insert(
     State(state): State<AppState>,
     Path(user_id): Path<String>,
     headers: HeaderMap,
-) -> Result<(), crate::Error> {
+    Json(registration_tokens): Json<Vec<String>>,
+) -> Result<Json<Vec<Member>>, crate::Error> {
     let user = get_user_from_header(&state.pool, &headers).await?;
     user.authorize(&state.pool, Some(Roles::ADMIN), Some(user_id))
         .await?;
 
-    Ok(())
+    let members =
+        DbMember::get_many_from_registration_tokens(&state.pool, registration_tokens).await?;
+
+    let member_ids: Vec<String> = members.iter().map(|m| m.member_id.to_owned()).collect();
+
+    let mut transaction = state.pool.begin().await?;
+
+    // Link the user to the members
+    let user_ids: Vec<uuid::Uuid> = vec![user.id; member_ids.len()];
+    DbUserMember::insert_many(&mut transaction, &user_ids, &member_ids).await?;
+
+    transaction.commit().await?;
+
+    Ok(Json(convert_vec(members)))
 }