diff --git a/ufl/algorithms/__init__.py b/ufl/algorithms/__init__.py
index 43eac078f..a2ca0ebb7 100644
--- a/ufl/algorithms/__init__.py
+++ b/ufl/algorithms/__init__.py
@@ -39,7 +39,6 @@
     "replace_terminal_data",
     "post_traversal",
     "change_to_reference_grad",
-    "expand_compounds",
     "validate_form",
     "FormSplitter",
     "extract_arguments",
@@ -71,7 +70,6 @@
 from ufl.algorithms.checks import validate_form
 from ufl.algorithms.compute_form_data import compute_form_data, preprocess_form
 from ufl.algorithms.estimate_degrees import estimate_total_polynomial_degree
-from ufl.algorithms.expand_compounds import expand_compounds
 from ufl.algorithms.expand_indices import expand_indices
 from ufl.algorithms.formfiles import load_forms, load_ufl_file, read_ufl_file
 from ufl.algorithms.formsplitter import FormSplitter
diff --git a/ufl/algorithms/expand_compounds.py b/ufl/algorithms/expand_compounds.py
deleted file mode 100644
index 0f2bc9d14..000000000
--- a/ufl/algorithms/expand_compounds.py
+++ /dev/null
@@ -1,24 +0,0 @@
-"""Algorithm for expanding compound expressions into equivalent representations."""
-
-# Copyright (C) 2008-2016 Martin Sandve Alnæs and Anders Logg
-#
-# This file is part of UFL (https://www.fenicsproject.org)
-#
-# SPDX-License-Identifier:    LGPL-3.0-or-later
-#
-# Modified by Anders Logg, 2009-2010
-
-import warnings
-
-from ufl.algorithms.apply_algebra_lowering import apply_algebra_lowering
-
-
-def expand_compounds(e):
-    """Expand compounds."""
-    warnings.warn(
-        "The use of expand_compounds is deprecated and will be removed after December 2023. "
-        "Please, use apply_algebra_lowering directly instead",
-        FutureWarning,
-    )
-
-    return apply_algebra_lowering(e)
diff --git a/ufl/compound_expressions.py b/ufl/compound_expressions.py
index 5eedfdedf..840397caa 100644
--- a/ufl/compound_expressions.py
+++ b/ufl/compound_expressions.py
@@ -7,7 +7,6 @@
 #
 # Modified by Anders Logg, 2009-2010
 
-import warnings
 
 from ufl.constantvalue import Zero, zero
 from ufl.core.multiindex import Index, indices
@@ -113,20 +112,6 @@ def determinant_expr_2x2(B):
     return _det_2x2(B, 0, 1, 0, 1)
 
 
-def old_determinant_expr_3x3(A):
-    """Determinant of a 3 by 3 matrix."""
-    warnings.warn(
-        "The use of old_determinant_expr_3x3 is deprecated and will be removed "
-        "after December 2023. Please, use determinant_expr_3x3 instead",
-        FutureWarning,
-    )
-    return (
-        A[0, 0] * _det_2x2(A, 1, 2, 1, 2)
-        + A[0, 1] * _det_2x2(A, 1, 2, 2, 0)
-        + A[0, 2] * _det_2x2(A, 1, 2, 0, 1)
-    )
-
-
 def determinant_expr_3x3(A):
     """Determinant of a 3 by 3 matrix."""
     return codeterminant_expr_nxn(A, [0, 1, 2], [0, 1, 2])
diff --git a/ufl/domain.py b/ufl/domain.py
index 50ee64d61..1b5544475 100644
--- a/ufl/domain.py
+++ b/ufl/domain.py
@@ -7,7 +7,6 @@
 # SPDX-License-Identifier:    LGPL-3.0-or-later
 
 import numbers
-import warnings
 
 from ufl.cell import AbstractCell
 from ufl.core.ufl_id import attach_ufl_id
@@ -220,36 +219,8 @@ def join_domains(domains):
         gdims.add(domain.geometric_dimension())
     if len(gdims) != 1:
         raise ValueError("Found domains with different geometric dimensions.")
-    (gdim,) = gdims
-
-    # Split into legacy and modern style domains
-    legacy_domains = []
-    modern_domains = []
-    for domain in domains:
-        if isinstance(domain, Mesh) and domain.ufl_id() < 0:
-            assert domain.ufl_cargo() is None
-            legacy_domains.append(domain)
-        else:
-            modern_domains.append(domain)
-
-    # Handle legacy domains checking
-    if legacy_domains:
-        warnings.warn(
-            "The use of Legacy domains will be deprecated by December 2023. "
-            "Please, use FunctionSpace instead",
-            DeprecationWarning,
-        )
-        if modern_domains:
-            raise ValueError(
-                "Found both a new-style domain and a legacy default domain. "
-                "These should not be used interchangeably. To find the legacy "
-                "domain, note that it is automatically created from a cell so "
-                "look for constructors taking a cell."
-            )
-        return tuple(legacy_domains)
 
-    # Handle modern domains checking (assuming correct by construction)
-    return tuple(modern_domains)
+    return domains
 
 
 # TODO: Move these to an analysis module?