diff --git a/account_constraints/__openerp__.py b/account_constraints/__openerp__.py
index 222b3e365..33de72c9f 100644
--- a/account_constraints/__openerp__.py
+++ b/account_constraints/__openerp__.py
@@ -48,6 +48,13 @@ Summary of constraints are:
 
 * Add a check on entries that user cannot provide a secondary currency
   if the same than the company one.
+  
+* Remove the possibility to modify or delete a move line related to an
+  invoice or a bank statement, no matter what the status of the move
+  (draft, validated or posted). This is usefule in standard context but
+  moreover if you're using : account_default_draft_move. This way you ensure
+  user cannot make mistake even in draft, he must pass through the 
+  parent object to make his modification.
 
     """,
     'website': 'http://www.camptocamp.com',
diff --git a/account_constraints/account_constraints.py b/account_constraints/account_constraints.py
index 861005daa..d1ecead4e 100644
--- a/account_constraints/account_constraints.py
+++ b/account_constraints/account_constraints.py
@@ -18,8 +18,8 @@
 #
 ##############################################################################
 
-from openerp.osv import fields, orm
-
+from openerp.osv import fields, orm, osv
+from openerp.tools.translate import _
 
 class AccountMove(orm.Model):
     _inherit = "account.move"
@@ -43,6 +43,53 @@ class AccountMove(orm.Model):
 class AccountMoveLine(orm.Model):
     _inherit = 'account.move.line'
 
+    def _check_invoice_related_move(self, cr, uid, ids, context=None):
+        for line in self.browse(cr, uid, ids, context=context):
+            if line.invoice:
+                err_msg = _('Invoice name (id): %s (%s)') % (line.invoice.name, str(line.invoice.id))
+                raise osv.except_osv(
+                    _('Error!'), 
+                    _('You cannot do this on an entry generated by an invoice. You must '
+                    'change the related invoice directly.\n%s.') % err_msg)
+        return True
+
+    def _check_statement_related_move(self, cr, uid, ids, context=None):
+        for line in self.browse(cr, uid, ids, context=context):
+            if line.statement_id:
+                err_msg = _('Bank statement name (id): %s (%s)') % (line.statement_id.name, str(line.statement_id.id))
+                raise osv.except_osv(
+                    _('Error!'), 
+                    _('You cannot do this on an entry generated by a bank statement. '
+                    'You must change the related bank statement directly.\n%s.') % err_msg)
+        return True
+
+    def unlink(self, cr, uid, ids, context=None, check=True):
+        """ Add the verification of:
+            - Is the move related to an invoice
+            - Is the move related to a bank statement
+            In that case, we forbid the move to be deleted even if draft. We should
+            never delete directly a move line related or generated by another object.
+            This is mandatory if you use the all move in draft (module: account_default_draft_move)
+            """
+        if not context.get('from_parent_object', False):
+            self._check_invoice_related_move(cr, uid, ids, context=context)
+            self._check_statement_related_move(cr, uid, ids, context=context)
+        return super(AccountMoveLine, self).unlink(cr, uid, ids, context=context, check=check)
+
+    def write(self, cr, uid, ids, vals, context=None, check=True, update_check=True):
+        """ Add the verification of:
+            - Is the move related to an invoice
+            - Is the move related to a bank statement
+            In that case, we forbid the move to be modified even if draft. We should
+            never update directly a move line related or generated by another object.
+            This is mandatory if you use the all move in draft (module: account_default_draft_move)
+            """
+        if not context.get('from_parent_object', False):
+            self._check_invoice_related_move(cr, uid, ids, context=context)
+            self._check_statement_related_move(cr, uid, ids, context=context)
+        return super(AccountMoveLine, self).write(cr, uid, ids, vals, 
+            context=context, check=check, update_check=update_check)
+
     def _check_currency_and_amount(self, cr, uid, ids, context=None):
         for l in self.browse(cr, uid, ids, context=context):
             if ((l.currency_id and not l.amount_currency) or
@@ -82,3 +129,38 @@ class AccountMoveLine(orm.Model):
              ['currency_id']
             ),
         ]
+
+
+class AccountInvoice(orm.Model):
+    _inherit = "account.invoice"
+    
+    def action_cancel(self, cr, uid, ids, context=None):
+        """Override the method to add the key 'from_parent_object' in
+        the context. This is to allow to delete move line related to invoice
+        through the buton cancel."""
+        if context is None:
+            context = {}
+        context['from_parent_object'] = True
+        return super(AccountInvoice, self).action_cancel(cr, uid, ids, context=context)
+
+
+class AccountBankStatement(orm.Model):
+    _inherit = "account.bank.statement"
+
+    def button_cancel(self, cr, uid, ids, context=None):
+        """Override the method to add the key 'from_parent_object' in
+        the context. This is to allow to delete move line related to bank statement
+        through the buton cancel."""
+        if context is None:
+            context = {}
+        context['from_parent_object'] = True
+        return super(AccountBankStatement, self).button_cancel(cr, uid, ids, context=context)
+
+    def create_move_from_st_line(self, cr, uid, st_line_id, company_currency_id, st_line_number, context=None):
+        """Add the from_parent_object key in context in order to be able to post the move."""
+        if context is None:
+            context = {}
+        context['from_parent_object'] = True
+        return super(AccountBankStatement, self).create_move_from_st_line(cr, uid, 
+            st_line_id, company_currency_id, st_line_number, context=context)
+