diff --git a/arho_feature_template/core/models.py b/arho_feature_template/core/models.py
index 8b12e67..e236430 100644
--- a/arho_feature_template/core/models.py
+++ b/arho_feature_template/core/models.py
@@ -146,6 +146,15 @@ def from_config_file(cls, config_fp: Path) -> RegulationGroupLibrary:
                 ],
             )
 
+    def get_short_names(self) -> set[str]:
+        """Returns set of non-empty short names (letter codes) of regulation groups part of the library."""
+        return {
+            regulation_group.short_name
+            for category in self.regulation_group_categories
+            for regulation_group in category.regulation_groups
+            if regulation_group.short_name
+        }
+
 
 @dataclass
 class RegulationLibrary:
diff --git a/arho_feature_template/core/plan_manager.py b/arho_feature_template/core/plan_manager.py
index 10f8088..b5c1f75 100644
--- a/arho_feature_template/core/plan_manager.py
+++ b/arho_feature_template/core/plan_manager.py
@@ -104,8 +104,7 @@ def __init__(self):
         self.regulation_groups_dock.new_regulation_group_requested.connect(self.create_new_regulation_group)
         self.regulation_groups_dock.edit_regulation_group_requested.connect(self.edit_regulation_group)
         self.regulation_groups_dock.delete_regulation_group_requested.connect(self.delete_regulation_group)
-        if get_active_plan_id():
-            self.regulation_groups_dock.initialize_regulation_groups(regulation_group_library_from_active_plan())
+        self.update_active_plan_regulation_group_library()
         self.regulation_groups_dock.hide()
 
         # Initialize digitize tools
@@ -156,6 +155,10 @@ def initialize_libraries(self):
         ]
         self.new_feature_dock.initialize_feature_template_libraries(self.feature_template_libraries)
 
+    def update_active_plan_regulation_group_library(self):
+        self.active_plan_regulation_group_library = regulation_group_library_from_active_plan()
+        self.regulation_groups_dock.update_regulation_groups(self.active_plan_regulation_group_library)
+
     def create_new_regulation_group(self):
         self._open_regulation_group_form(RegulationGroup())
 
@@ -163,17 +166,17 @@ def edit_regulation_group(self, regulation_group: RegulationGroup):
         self._open_regulation_group_form(regulation_group)
 
     def _open_regulation_group_form(self, regulation_group: RegulationGroup):
-        regulation_group_form = PlanRegulationGroupForm(regulation_group)
+        regulation_group_form = PlanRegulationGroupForm(regulation_group, self.active_plan_regulation_group_library)
         if regulation_group_form.exec_():
             if regulation_group_form.save_as_config:
                 save_regulation_group_as_config(regulation_group_form.model)
             else:
                 save_regulation_group(regulation_group_form.model)
-            self.regulation_groups_dock.initialize_regulation_groups(regulation_group_library_from_active_plan())
+            self.update_active_plan_regulation_group_library()
 
     def delete_regulation_group(self, group: RegulationGroup):
         delete_regulation_group(group)
-        self.regulation_groups_dock.initialize_regulation_groups(regulation_group_library_from_active_plan())
+        self.update_active_plan_regulation_group_library()
 
     def toggle_identify_plan_features(self, activate: bool):  # noqa: FBT001
         if activate:
@@ -240,7 +243,7 @@ def edit_plan(self):
         attribute_form = PlanAttributeForm(plan_model, self.regulation_group_libraries)
         if attribute_form.exec_():
             feature = save_plan(attribute_form.model)
-            self.regulation_groups_dock.initialize_regulation_groups(regulation_group_library_from_active_plan())
+            self.update_active_plan_regulation_group_library()
 
     def edit_lifecycles(self):
         plan_layer = PlanLayer.get_from_project()
@@ -311,11 +314,11 @@ def _plan_feature_geom_digitized(self, feature: QgsFeature):
 
         plan_feature.geom = feature.geometry()
         attribute_form = PlanFeatureForm(
-            plan_feature, title, [*self.regulation_group_libraries, regulation_group_library_from_active_plan()]
+            plan_feature, title, self.regulation_group_libraries, self.active_plan_regulation_group_library
         )
         if attribute_form.exec_():
             save_plan_feature(attribute_form.model)
-            self.regulation_groups_dock.initialize_regulation_groups(regulation_group_library_from_active_plan())
+            self.update_active_plan_regulation_group_library()
 
     def edit_plan_feature(self, feature: QgsFeature, layer_name: str):
         layer_class = FEATURE_LAYER_NAME_TO_CLASS_MAP[layer_name]
@@ -323,11 +326,11 @@ def edit_plan_feature(self, feature: QgsFeature, layer_name: str):
 
         title = plan_feature.name if plan_feature.name else layer_name
         attribute_form = PlanFeatureForm(
-            plan_feature, title, [*self.regulation_group_libraries, regulation_group_library_from_active_plan()]
+            plan_feature, title, self.regulation_group_libraries, self.active_plan_regulation_group_library
         )
         if attribute_form.exec_():
             save_plan_feature(attribute_form.model)
-            self.regulation_groups_dock.initialize_regulation_groups(regulation_group_library_from_active_plan())
+            self.update_active_plan_regulation_group_library()
 
     def set_active_plan(self, plan_id: str | None):
         """Update the project layers based on the selected land use plan.
@@ -352,8 +355,7 @@ def set_active_plan(self, plan_id: str | None):
         if previously_in_edit_mode:
             plan_layer.startEditing()
 
-        # Update regulation group dock
-        self.regulation_groups_dock.initialize_regulation_groups(regulation_group_library_from_active_plan())
+        self.update_active_plan_regulation_group_library()
 
     def load_land_use_plan(self):
         """Load an existing land use plan using a dialog selection."""
@@ -456,6 +458,11 @@ def unload(self):
 
 
 def regulation_group_library_from_active_plan() -> RegulationGroupLibrary:
+    if not get_active_plan_id():
+        return RegulationGroupLibrary(
+            name="Käytössä olevat kaavamääräysryhmät", version=None, description=None, regulation_group_categories=[]
+        )
+
     id_of_general_regulation_group_type = PlanRegulationGroupTypeLayer.get_attribute_value_by_another_attribute_value(
         "id", "value", "generalRegulations"
     )
diff --git a/arho_feature_template/gui/dialogs/plan_feature_form.py b/arho_feature_template/gui/dialogs/plan_feature_form.py
index d945fd8..1c1e24d 100644
--- a/arho_feature_template/gui/dialogs/plan_feature_form.py
+++ b/arho_feature_template/gui/dialogs/plan_feature_form.py
@@ -10,6 +10,7 @@
     QDialog,
     QDialogButtonBox,
     QLineEdit,
+    QMessageBox,
     QScrollArea,
     QSizePolicy,
     QSpacerItem,
@@ -39,7 +40,11 @@ class PlanFeatureForm(QDialog, FormClass):  # type: ignore
     """Parent class for feature forms for adding and modifying feature attribute data."""
 
     def __init__(
-        self, plan_feature: PlanFeature, form_title: str, regulation_group_libraries: list[RegulationGroupLibrary]
+        self,
+        plan_feature: PlanFeature,
+        form_title: str,
+        regulation_group_libraries: list[RegulationGroupLibrary],
+        active_plan_regulation_groups_library: RegulationGroupLibrary,
     ):
         super().__init__()
         self.setupUi(self)
@@ -57,7 +62,9 @@ def __init__(
         self.regulation_groups_tree_layout: QVBoxLayout
 
         # INIT
-        self.regulation_group_libraries = regulation_group_libraries
+        self.existing_group_short_names = active_plan_regulation_groups_library.get_short_names()
+        self.active_plan_regulation_groups_library = active_plan_regulation_groups_library
+        self.regulation_group_libraries = [*regulation_group_libraries, active_plan_regulation_groups_library]
         self.plan_regulation_group_libraries_combobox.addItems(
             library.name for library in self.regulation_group_libraries
         )
@@ -97,6 +104,44 @@ def _remove_spacer(self):
             self.plan_regulation_group_scrollarea_contents.layout().removeItem(self.scroll_area_spacer)
             self.scroll_area_spacer = None
 
+    def _check_regulation_group_short_names(self) -> bool:
+        seen_names = set()
+        existing_names = set()
+        duplicate_names = set()
+
+        for reg_group_widget in self.regulation_group_widgets:
+            short_name = reg_group_widget.short_name.text()
+            if not short_name:
+                continue
+
+            if short_name in self.existing_group_short_names:
+                existing_names.add(short_name)
+            if short_name in seen_names:
+                duplicate_names.add(short_name)
+            seen_names.add(short_name)
+
+        def format_names(names, last_item_conjucation: str = "ja"):
+            names = list(names)
+            formatted_names = ", ".join(f"'<b>{name}</b>'" for name in names[:-1])
+            formatted_names += f" {last_item_conjucation} " if len(names) > 1 else ""
+            formatted_names += f"'<b>{names[-1]}</b>'" if names else ""
+            return formatted_names
+
+        if existing_names:
+            if len(existing_names) == 1:
+                msg = f"Kaavamääräysryhmä lyhyellä nimellä {format_names(existing_names)} on jo olemassa."
+            else:
+                msg = f"Kaavamääräysryhmät lyhyillä nimillä {format_names(existing_names)} ovat jo olemassa."
+            QMessageBox.critical(self, "Virhe", msg)
+            return False
+
+        if duplicate_names:
+            msg = f"Lomakkeella on useita kaavamääräysryhmiä, joilla on lyhyt nimi {format_names(duplicate_names, 'tai')}."
+            QMessageBox.critical(self, "Virhe", msg)
+            return False
+
+        return True
+
     def add_selected_plan_regulation_group(self, item: QTreeWidgetItem, column: int):
         if not item.parent():
             return
@@ -113,7 +158,9 @@ def add_plan_regulation_group(self, definition: RegulationGroup):
         self._add_spacer()
 
     def open_plan_regulation_group_form(self, regulation_group_widget: RegulationGroupWidget):
-        group_as_form = PlanRegulationGroupForm(regulation_group_widget.into_model())
+        group_as_form = PlanRegulationGroupForm(
+            regulation_group_widget.into_model(), self.active_plan_regulation_groups_library
+        )
         if group_as_form.exec_():
             regulation_group_widget.from_model(group_as_form.model)
 
@@ -146,5 +193,6 @@ def into_model(self) -> PlanFeature:
         )
 
     def _on_ok_clicked(self):
-        self.model = self.into_model()
-        self.accept()
+        if self._check_regulation_group_short_names():
+            self.model = self.into_model()
+            self.accept()
diff --git a/arho_feature_template/gui/dialogs/plan_regulation_group_form.py b/arho_feature_template/gui/dialogs/plan_regulation_group_form.py
index 4053060..a7bf234 100644
--- a/arho_feature_template/gui/dialogs/plan_regulation_group_form.py
+++ b/arho_feature_template/gui/dialogs/plan_regulation_group_form.py
@@ -12,6 +12,7 @@
     QDialogButtonBox,
     QHBoxLayout,
     QLabel,
+    QMessageBox,
     QSizePolicy,
     QTextBrowser,
     QTreeWidgetItem,
@@ -23,6 +24,7 @@
     Regulation,
     RegulationConfig,
     RegulationGroup,
+    RegulationGroupLibrary,
     RegulationLibrary,
 )
 from arho_feature_template.gui.components.plan_proposition_widget import PropositionWidget
@@ -45,7 +47,9 @@
 class PlanRegulationGroupForm(QDialog, FormClass):  # type: ignore
     """Form to create a new plan regulation group."""
 
-    def __init__(self, regulation_group: RegulationGroup):
+    def __init__(
+        self, regulation_group: RegulationGroup, active_plan_regulation_groups_library: RegulationGroupLibrary
+    ):
         super().__init__()
         self.setupUi(self)
 
@@ -74,6 +78,7 @@ def __init__(self, regulation_group: RegulationGroup):
         self.regulation_widgets: list[RegulationWidget] = []
         self.proposition_widgets: list[PropositionWidget] = []
         self.save_as_config = False
+        self.existing_group_short_names = active_plan_regulation_groups_library.get_short_names()
 
         # Initialize regulation library
         self.regulations_selection_widget = TreeWithSearchWidget()
@@ -137,6 +142,14 @@ def _initalize_regulation_from_config(self, config: RegulationConfig, parent: QT
         for child_config in config.child_regulations:
             self._initalize_regulation_from_config(child_config, item)
 
+    def _check_short_name(self) -> bool:
+        short_name = self.short_name.text()
+        if short_name and short_name in self.existing_group_short_names:
+            msg = f"Kaavamääräysryhmä lyhyellä nimellä '<b>{short_name}</b>' on jo olemassa."
+            QMessageBox.critical(self, "Virhe", msg)
+            return False
+        return True
+
     def update_selected_regulation(self, item: QTreeWidgetItem, column: int):
         config: RegulationConfig = item.data(column, Qt.UserRole)  # Retrieve the associated config
         self.regulation_info.setText(config.description)
@@ -190,5 +203,6 @@ def into_model(self) -> RegulationGroup:
         )
 
     def _on_ok_clicked(self):
-        self.model = self.into_model()
-        self.accept()
+        if self._check_short_name():
+            self.model = self.into_model()
+            self.accept()
diff --git a/arho_feature_template/gui/docks/regulation_groups_dock.py b/arho_feature_template/gui/docks/regulation_groups_dock.py
index 6e525a6..b388dd7 100644
--- a/arho_feature_template/gui/docks/regulation_groups_dock.py
+++ b/arho_feature_template/gui/docks/regulation_groups_dock.py
@@ -64,7 +64,7 @@ def connect_buttons(self):
         self.edit_btn.clicked.connect(self.on_edit_btn_clicked)
         self.delete_btn.clicked.connect(self.on_delete_btn_clicked)
 
-    def initialize_regulation_groups(self, regulation_group_library: RegulationGroupLibrary):
+    def update_regulation_groups(self, regulation_group_library: RegulationGroupLibrary):
         self.regulation_group_list.clear()
 
         for category in regulation_group_library.regulation_group_categories: