diff --git a/saphyr/node.cc b/saphyr/node.cc
index 8cd6aba..4c982f8 100644
--- a/saphyr/node.cc
+++ b/saphyr/node.cc
@@ -125,20 +125,20 @@ size_t Node::size() const { return node_.len(); }
 bool Node::IsEmpty() const { return node_.is_empty(); }
 Node::operator bool() const { return IsDefined(); }
 
-NodeView Node::operator[](rs_std::StrRef key) const {
+NodeView Node::operator[](rs_std::StrRef key) const& {
   return NodeView(node_.get_at_key(key).value_or(rust::NodeView()));
 }
-NodeView Node::operator[](size_t index) const {
+NodeView Node::operator[](size_t index) const& {
   return NodeView(node_.get_at_index(index).value_or(rust::NodeView()));
 }
-std::optional<NodeView> Node::Get(size_t index) const {
+std::optional<NodeView> Node::Get(size_t index) const& {
   if (auto val = node_.get_at_index(index)) {
     return std::make_optional(NodeView(*val));
   }
   return std::nullopt;
 }
 
-std::optional<NodeView> Node::Get(rs_std::StrRef key) const {
+std::optional<NodeView> Node::Get(rs_std::StrRef key) const& {
   if (auto val = node_.get_at_key(key)) {
     return std::make_optional(NodeView(*val));
   }
@@ -150,7 +150,7 @@ void Node::SetAtIndex(size_t index, rust::YamlOwned value) {
 }
 
 template <>
-std::optional<int> Node::as_optional<int>() const {
+std::optional<int> Node::as_optional<int>() const& {
   auto v = node_.as_i64();
   if (!v) return std::nullopt;
   if (*v < std::numeric_limits<int>::min() ||
@@ -161,28 +161,28 @@ std::optional<int> Node::as_optional<int>() const {
 }
 
 template <>
-std::optional<size_t> Node::as_optional<size_t>() const {
+std::optional<size_t> Node::as_optional<size_t>() const& {
   auto v = node_.as_i64();
   if (!v || *v < 0) return std::nullopt;
   return static_cast<size_t>(*v);
 }
 
 template <>
-std::optional<bool> Node::as_optional<bool>() const {
+std::optional<bool> Node::as_optional<bool>() const& {
   return node_.as_bool();
 }
 
 template <>
-std::optional<absl::string_view> Node::as_optional<absl::string_view>() const {
+std::optional<absl::string_view> Node::as_optional<absl::string_view>() const& {
   return node_.as_str();
 }
 
 template <>
-std::optional<double> Node::as_optional<double>() const {
+std::optional<double> Node::as_optional<double>() const& {
   return node_.as_f64();
 }
 
-NodeView Node::as_view() const { return NodeView(node_.as_view()); }
+NodeView Node::as_view() const& { return NodeView(node_.as_view()); }
 
 absl::StatusOr<std::string> Dump(const Node& node) {
   return node.as_view().Dump();
diff --git a/saphyr/node.h b/saphyr/node.h
index 1e3e85d..f6f4a8f 100644
--- a/saphyr/node.h
+++ b/saphyr/node.h
@@ -211,27 +211,36 @@ class Node {
   // Accesses an element in a map by key.
   // Returns a `NodeView` for which `IsDefined()` is false if the node is not a
   // map or the key is not found.
-  NodeView operator[](rs_std::StrRef key) const ABSL_ATTRIBUTE_LIFETIME_BOUND;
-  NodeView operator[](const char* key) const ABSL_ATTRIBUTE_LIFETIME_BOUND {
+  NodeView operator[](rs_std::StrRef key) const& ABSL_ATTRIBUTE_LIFETIME_BOUND;
+  NodeView operator[](const char* key) const& ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return operator[](rs_std::StrRef::FromUtf8Unchecked(key));
   }
-  NodeView operator[](absl::string_view key) const
-      ABSL_ATTRIBUTE_LIFETIME_BOUND {
+  NodeView operator[](
+      absl::string_view key) const& ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return operator[](rs_std::StrRef::FromUtf8Unchecked(key));
   }
+  NodeView operator[](rs_std::StrRef key) const&& = delete;
+  NodeView operator[](const char* key) const&& = delete;
+  NodeView operator[](absl::string_view key) const&& = delete;
+
   // Accesses an element in a sequence by index.
   // Returns a `NodeView` for which `IsDefined()` is false if the node is not a
   // sequence or the index is out of bounds.
-  NodeView operator[](size_t index) const ABSL_ATTRIBUTE_LIFETIME_BOUND;
-  NodeView operator[](int index) const ABSL_ATTRIBUTE_LIFETIME_BOUND {
+  NodeView operator[](size_t index) const& ABSL_ATTRIBUTE_LIFETIME_BOUND;
+  NodeView operator[](int index) const& ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return index < 0 ? NodeView() : operator[](static_cast<size_t>(index));
   }
+  NodeView operator[](size_t index) const&& = delete;
+  NodeView operator[](int index) const&& = delete;
 
   // A safer version of `operator[]` for sequence.
-  std::optional<NodeView> Get(size_t index) const ABSL_ATTRIBUTE_LIFETIME_BOUND;
+  std::optional<NodeView> Get(
+      size_t index) const& ABSL_ATTRIBUTE_LIFETIME_BOUND;
   // A safer version of `operator[]` for map.
-  std::optional<NodeView> Get(rs_std::StrRef key) const
-      ABSL_ATTRIBUTE_LIFETIME_BOUND;
+  std::optional<NodeView> Get(
+      rs_std::StrRef key) const& ABSL_ATTRIBUTE_LIFETIME_BOUND;
+  std::optional<NodeView> Get(size_t index) const&& = delete;
+  std::optional<NodeView> Get(rs_std::StrRef key) const&& = delete;
 
   // Sets the value at a given index in a sequence.
   // If `index` is within bounds, the existing value is replaced.
@@ -242,10 +251,13 @@ class Node {
   // Tries to convert the node to the specified type `T`.
   // Returns `std::nullopt` if the conversion fails or the node is undefined.
   template <typename T>
-  std::optional<T> as_optional() const;
+  std::optional<T> as_optional() const&;
+  template <typename T>
+  std::optional<T> as_optional() const&& = delete;
 
   // Returns a view into the node.
-  NodeView as_view() const ABSL_ATTRIBUTE_LIFETIME_BOUND;
+  NodeView as_view() const& ABSL_ATTRIBUTE_LIFETIME_BOUND;
+  NodeView as_view() const&& = delete;
 
  private:
   rust::NodeOwned node_;