diff --git a/src/webui/gitutils.jl b/src/webui/gitutils.jl
index 885686ae75..9e68c4b1ff 100644
--- a/src/webui/gitutils.jl
+++ b/src/webui/gitutils.jl
@@ -25,13 +25,31 @@ getrepo(::GitLabAPI, owner::AbstractString, name::AbstractString) =
 getrepo(::GitHubAPI, owner::AbstractString, name::AbstractString) =
     @gf get_repo(PROVIDERS["github"].client, owner, name)
 
+
+abstract type AuthResult end
+struct AuthSuccess <: AuthResult end
+struct AuthFailure <: AuthResult
+    reason::AbstractString
+end
+
+function AuthResult(res::Union{Bool,Nothing}, reason_for_failure::AbstractString)
+    if res === nothing || !res
+        return AuthFailure(reason_for_failure)
+    else
+        return AuthSuccess()
+    end
+end
+
+is_success(res::AuthSuccess) = true
+is_success(res::AuthFailure) = false
+
 # Check for a user's authorization to release a package.
 # The criteria is simply whether the user is a collaborator for user-owned repos,
 # or whether they're an organization member or collaborator for organization-owned repos.
-isauthorized(u, repo) = false
+isauthorized(u, repo) = AuthFailure("Unkown user type / repo type")
 function isauthorized(u::User{GitHub.User}, repo::GitHub.Repo)
     if !get(CONFIG, "allow_private", false)
-        repo.private && return false
+        return AuthResult(!repo.private, "Repo $(repo.name) is private")
     end
 
     if repo.private
@@ -40,20 +58,21 @@ function isauthorized(u::User{GitHub.User}, repo::GitHub.Repo)
         forge = u.forge
     end
 
-    hasauth = if repo.organization === nothing
-        @gf is_collaborator(forge, repo.owner.login, repo.name, u.user.login)
+    if repo.organization === nothing
+        hasauth = @gf is_collaborator(forge, repo.owner.login, repo.name, u.user.login)
+        return AuthResult(hasauth, "User $(u.user.name) is not a collaborator on repo $(repo.name)")
     else
         # First check for organization membership, and fall back to collaborator status.
         ismember = @gf is_member(forge, repo.organization.login, u.user.login)
-        something(ismember, false) ||
+        hasauth = something(ismember, false) ||
             @gf is_collaborator(forge, repo.organization.login, repo.name, u.user.login)
+        return AuthResult(hasauth, "User $(u.user.name) is not part of the org $(repo.organization.login) and not a collaborator on repo $(repo.name)")
     end
-    return something(hasauth, false)
 end
 
 function isauthorized(u::User{GitLab.User}, repo::GitLab.Project)
     if !get(CONFIG, "allow_private", false)
-        repo.visibility == "private" && return false
+        return AuthResult(repo.visibility !== "private", "Project $(repo.name) is private")
     end
 
     if repo.visibility == "private"
@@ -62,8 +81,9 @@ function isauthorized(u::User{GitLab.User}, repo::GitLab.Project)
         forge = u.forge
     end
 
-    hasauth = if repo.namespace.kind == "user"
-        @gf is_collaborator(forge, repo.owner.username, repo.name, u.user.id)
+    if repo.namespace.kind == "user"
+        hasauth = @gf is_collaborator(forge, repo.owner.username, repo.name, u.user.id)
+        return AuthResult(hasauth, "User $(u.user.name) is not a member of project $(repo.name)")
     else
         # Same as above: group membership then collaborator check.
         nspath = split(repo.namespace.full_path, "/")
@@ -76,9 +96,8 @@ function isauthorized(u::User{GitLab.User}, repo::GitLab.Project)
                 something(ismember, false) && break
             end
         end
-        ismember
+        return AuthResult(ismember, "Project $(repo.name) belongs to the group $(repo.namespace.full_path), and user $(u.user.name) is not a member of that group or its parent group(s)")
     end
-    return something(hasauth, false)
 end
 
 # Get the raw (Julia)Project.toml text from a repository.
diff --git a/src/webui/routes/register.jl b/src/webui/routes/register.jl
index f5a752796f..3cabe71ebb 100644
--- a/src/webui/routes/register.jl
+++ b/src/webui/routes/register.jl
@@ -30,7 +30,10 @@ function register(r::HTTP.Request)
     owner, name = splitrepo(package)
     repo = getrepo(u.forge, owner, name)
     repo === nothing && return json(400; error="Repository was not found")
-    isauthorized(u, repo) || return json(400; error="Unauthorized to release this package")
+    auth_result = isauthorized(u, repo)
+    if !is_success(auth_result)
+        return json(400; error="Unauthorized to release this package. Reason: $(auth_result.reason)")
+    end
 
     # Get the (Julia)Project.toml, and make sure it is valid.
     toml = gettoml(u.forge, repo, ref)