diff --git a/Library/Homebrew/brew.rb b/Library/Homebrew/brew.rb
index 6898eff1f13e0..59cb5e11a0103 100644
--- a/Library/Homebrew/brew.rb
+++ b/Library/Homebrew/brew.rb
@@ -211,8 +211,13 @@
     $stderr.puts "If reporting this issue please do so at (not Homebrew/brew or Homebrew/homebrew-core):"
     $stderr.puts "  #{Formatter.url(issues_url)}"
   elsif internal_cmd
-    $stderr.puts "#{Tty.bold}Please report this issue:#{Tty.reset}"
-    $stderr.puts "  #{Formatter.url(OS::ISSUES_URL)}"
+    if e.is_a?(MethodDeprecatedError) && (first_backtrace = e.backtrace&.first.presence) &&
+       (first_backtrace.include?("/formulary.rb") || first_backtrace.include?("/cask_loader.rb"))
+      $stderr.puts Utils::Backtrace.clean(e) if ARGV.include?("--debug") || args.debug?
+    else
+      $stderr.puts "#{Tty.bold}Please report this issue:#{Tty.reset}"
+      $stderr.puts "  #{Formatter.url(OS::ISSUES_URL)}"
+    end
   end
 
   exit 1
diff --git a/Library/Homebrew/cask/cask_loader.rb b/Library/Homebrew/cask/cask_loader.rb
index a91882a6e5049..af0949f853e98 100644
--- a/Library/Homebrew/cask/cask_loader.rb
+++ b/Library/Homebrew/cask/cask_loader.rb
@@ -105,10 +105,19 @@ def self.try_new(ref, warn: false)
         end
 
         return if %w[.rb .json].exclude?(path.extname)
+        return if path.to_s.include?("/Formula/")
         return unless path.expand_path.exist?
 
-        return if Homebrew::EnvConfig.forbid_packages_from_paths? &&
-                  !path.realpath.to_s.start_with?("#{Caskroom.path}/", "#{HOMEBREW_LIBRARY}/Taps/")
+        unless path.realpath.to_s.start_with?("#{Caskroom.path}/", "#{HOMEBREW_LIBRARY}/Taps/",
+                                              "#{HOMEBREW_LIBRARY_PATH}/test/support/fixtures/")
+          return if Homebrew::EnvConfig.forbid_packages_from_paths?
+
+          # So many tests legimately use casks from paths that we can't warn about them all.
+          # Let's focus on end-users for now.
+          unless ENV["HOMEBREW_TESTS"]
+            odeprecated "installing formulae from paths or URLs", "installing formulae from taps"
+          end
+        end
 
         new(path)
       end
@@ -195,6 +204,8 @@ def initialize(url)
       def load(config:)
         path.dirname.mkpath
 
+        odeprecated "installing casks from paths or URLs", "installing casks from taps"
+
         if ALLOWED_URL_SCHEMES.exclude?(url.scheme)
           raise UnsupportedInstallationMethod,
                 "Non-checksummed download of #{name} formula file from an arbitrary URL is unsupported! " \
diff --git a/Library/Homebrew/formulary.rb b/Library/Homebrew/formulary.rb
index 67ae6b78ad7c7..621fe1dcd2370 100644
--- a/Library/Homebrew/formulary.rb
+++ b/Library/Homebrew/formulary.rb
@@ -646,9 +646,6 @@ def self.try_new(ref, from: T.unsafe(nil), warn: false)
 
       return unless path.expand_path.exist?
 
-      return if Homebrew::EnvConfig.forbid_packages_from_paths? &&
-                !path.realpath.to_s.start_with?("#{HOMEBREW_CELLAR}/", "#{HOMEBREW_LIBRARY}/Taps/")
-
       options = if (tap = Tap.from_path(path))
         # Only treat symlinks in taps as aliases.
         if path.symlink?
@@ -675,6 +672,17 @@ def self.try_new(ref, from: T.unsafe(nil), warn: false)
 
       return if path.extname != ".rb"
 
+      unless path.realpath.to_s.start_with?("#{HOMEBREW_CELLAR}/", "#{HOMEBREW_TAP_DIRECTORY}/",
+                                            "#{HOMEBREW_LIBRARY_PATH}/test/support/fixtures/")
+        return if Homebrew::EnvConfig.forbid_packages_from_paths?
+
+        # So many tests legimately use formulae from paths that we can't warn about them all.
+        # Let's focus on end-users for now.
+        unless ENV["HOMEBREW_TESTS"]
+          odeprecated "installing formulae from paths or URLs", "installing formulae from taps"
+        end
+      end
+
       new(path, **options)
     end
 
@@ -716,6 +724,8 @@ def self.try_new(ref, from: T.unsafe(nil), warn: false)
       return unless uri.path
       return unless uri.scheme.present?
 
+      odeprecated "installing formulae from paths or URLs", "installing formulae from taps"
+
       new(uri, from:)
     end
 
diff --git a/Library/Homebrew/test/cask/cask_loader/from_uri_loader_spec.rb b/Library/Homebrew/test/cask/cask_loader/from_uri_loader_spec.rb
index d1777c9f6dcaa..60db335071828 100644
--- a/Library/Homebrew/test/cask/cask_loader/from_uri_loader_spec.rb
+++ b/Library/Homebrew/test/cask/cask_loader/from_uri_loader_spec.rb
@@ -29,28 +29,28 @@
       loader = described_class.new("https://brew.sh/foo.rb")
       expect do
         loader.load(config: nil)
-      end.to raise_error(UnsupportedInstallationMethod)
+      end.to raise_error(MethodDeprecatedError)
     end
 
     it "raises an error when given an ftp URL" do
       loader = described_class.new("ftp://brew.sh/foo.rb")
       expect do
         loader.load(config: nil)
-      end.to raise_error(UnsupportedInstallationMethod)
+      end.to raise_error(MethodDeprecatedError)
     end
 
     it "raises an error when given an sftp URL" do
       loader = described_class.new("sftp://brew.sh/foo.rb")
       expect do
         loader.load(config: nil)
-      end.to raise_error(UnsupportedInstallationMethod)
+      end.to raise_error(MethodDeprecatedError)
     end
 
-    it "does not raise an error when given a file URL" do
+    it "raises an error when given a file URL" do
       loader = described_class.new("file://#{TEST_FIXTURE_DIR}/cask/Casks/local-caffeine.rb")
       expect do
         loader.load(config: nil)
-      end.not_to raise_error(UnsupportedInstallationMethod)
+      end.to raise_error(MethodDeprecatedError)
     end
   end
 end
diff --git a/Library/Homebrew/test/cask/cask_spec.rb b/Library/Homebrew/test/cask/cask_spec.rb
index 038316a682715..ccb0f23da273e 100644
--- a/Library/Homebrew/test/cask/cask_spec.rb
+++ b/Library/Homebrew/test/cask/cask_spec.rb
@@ -46,16 +46,10 @@
       expect(c.token).to eq("caffeine")
     end
 
-    it "returns an instance of the Cask from a URL", :needs_utils_curl, :no_api do
-      c = Cask::CaskLoader.load("file://#{tap_path}/Casks/local-caffeine.rb")
-      expect(c).to be_a(described_class)
-      expect(c.token).to eq("local-caffeine")
-    end
-
     it "raises an error when failing to download a Cask from a URL", :needs_utils_curl, :no_api do
       expect do
         Cask::CaskLoader.load("file://#{tap_path}/Casks/notacask.rb")
-      end.to raise_error(Cask::CaskUnavailableError)
+      end.to raise_error(MethodDeprecatedError)
     end
 
     it "returns an instance of the Cask from a relative file location" do
diff --git a/Library/Homebrew/test/formulary_spec.rb b/Library/Homebrew/test/formulary_spec.rb
index 3e344cad5c30f..1066f66d097c3 100644
--- a/Library/Homebrew/test/formulary_spec.rb
+++ b/Library/Homebrew/test/formulary_spec.rb
@@ -129,11 +129,6 @@ class Wrong#{described_class.class_s(formula_name)} < Formula
         end.to raise_error(FormulaUnavailableError)
       end
 
-      it "returns a Formula when given a URL", :needs_utils_curl, :no_api do
-        formula = described_class.factory("file://#{formula_path}")
-        expect(formula).to be_a(Formula)
-      end
-
       it "errors when given a URL but paths are disabled" do
         ENV["HOMEBREW_FORBID_PACKAGES_FROM_PATHS"] = "1"
         expect do
@@ -546,31 +541,31 @@ def formula_json_contents(extra_items = {})
       it "raises an error when given an https URL" do
         expect do
           described_class.factory("https://brew.sh/foo.rb")
-        end.to raise_error(UnsupportedInstallationMethod)
+        end.to raise_error(MethodDeprecatedError)
       end
 
       it "raises an error when given a bottle URL" do
         expect do
           described_class.factory("https://brew.sh/foo-1.0.arm64_catalina.bottle.tar.gz")
-        end.to raise_error(UnsupportedInstallationMethod)
+        end.to raise_error(MethodDeprecatedError)
       end
 
       it "raises an error when given an ftp URL" do
         expect do
           described_class.factory("ftp://brew.sh/foo.rb")
-        end.to raise_error(UnsupportedInstallationMethod)
+        end.to raise_error(MethodDeprecatedError)
       end
 
       it "raises an error when given an sftp URL" do
         expect do
           described_class.factory("sftp://brew.sh/foo.rb")
-        end.to raise_error(UnsupportedInstallationMethod)
+        end.to raise_error(MethodDeprecatedError)
       end
 
-      it "does not raise an error when given a file URL" do
+      it "raises an error when given a file URL" do
         expect do
           described_class.factory("file://#{TEST_FIXTURE_DIR}/testball.rb")
-        end.not_to raise_error(UnsupportedInstallationMethod)
+        end.to raise_error(MethodDeprecatedError)
       end
     end