diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 82b59bf..327a824 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -61,36 +61,3 @@ jobs:
           echo "::group::Tests (w/ phar composer/composer)"
           COMPOSER_AUDIT_TEST_COMPOSER_BINARY=$(which composer) vendor/bin/simple-phpunit --verbose
           echo "::endgroup::"
-  # Verifies that the plugin entry point still parses on PHP 5.3, users of 5.3
-  # cannot use this Composer plugin but at least it won't break their Composer.
-  legacy:
-    runs-on: ubuntu-latest
-    name: PHP 5.3
-    steps:
-      - uses: actions/checkout@v2
-      - uses: shivammathur/setup-php@d30ad8b1843ace22e6698ab99bbafaa747b6bd0d
-        with:
-          php-version: 5.3
-          tools: composer:2.2
-          coverage: none
-      - name: Syntax check
-        run: |
-          while read file; do
-            php -l "$file"
-          done < <(find src/Legacy -type f -name "*.php")
-      - name: Integration test
-        run: |
-          composer global config allow-plugins.cs278/composer-audit true
-          composer global config repositories.0 path "$(pwd)"
-          composer global require --ignore-platform-reqs symfony/yaml '~4.4'
-          composer global require --ignore-platform-reqs cs278/composer-audit '*@dev'
-
-          set +e
-          composer global audit -vvv
-          result=$?
-          set -e
-
-          if [ $result -ne 2 ]; then
-            echo "Expected audit command to exit with error code 2, got: ${result}" >&2
-            exit 1
-          fi
diff --git a/composer.json b/composer.json
index 4e6f3ef..2355fc3 100644
--- a/composer.json
+++ b/composer.json
@@ -11,8 +11,8 @@
     ],
     "minimum-stability": "stable",
     "require": {
-        "php": ">= 7.1",
-        "composer-plugin-api": "^1.1 || ^2",
+        "php": ">= 7.2",
+        "composer-plugin-api": "^2",
         "symfony/yaml": "^4.4 || ^5 || ^6 || ^7"
     },
     "require-dev": {
@@ -35,6 +35,6 @@
         "sort-packages": true
     },
     "extra": {
-        "class": "Cs278\\ComposerAudit\\Legacy\\ComposerPlugin"
+        "class": "Cs278\\ComposerAudit\\ComposerPlugin"
     }
 }
diff --git a/src/AdvisoriesInstallerV1.php b/src/AdvisoriesInstallerV1.php
deleted file mode 100644
index 8bbc5ac..0000000
--- a/src/AdvisoriesInstallerV1.php
+++ /dev/null
@@ -1,29 +0,0 @@
-<?php
-
-namespace Cs278\ComposerAudit;
-
-use Composer\Downloader\DownloadManager;
-use Composer\Package\PackageInterface;
-use Composer\Repository\RepositoryManager;
-
-/**
- * @copyright 2020 Chris Smith
- * @license MIT
- */
-final class AdvisoriesInstallerV1 extends AdvisoriesInstaller
-{
-    /** @var DownloadManager */
-    private $downloadManager;
-
-    public function __construct(RepositoryManager $repositoryManager, DownloadManager $downloadManager)
-    {
-        parent::__construct($repositoryManager);
-
-        $this->downloadManager = $downloadManager;
-    }
-
-    protected function downloadAndInstall($targetDirectory, PackageInterface $package)
-    {
-        $this->downloadManager->download($package, $targetDirectory, false);
-    }
-}
diff --git a/src/Legacy/AuditNotCompatibleCommand.php b/src/Legacy/AuditNotCompatibleCommand.php
deleted file mode 100644
index d389a61..0000000
--- a/src/Legacy/AuditNotCompatibleCommand.php
+++ /dev/null
@@ -1,47 +0,0 @@
-<?php
-
-namespace Cs278\ComposerAudit\Legacy;
-
-use Composer\Command\BaseCommand;
-use Symfony\Component\Console\Input\InputInterface;
-use Symfony\Component\Console\Input\InputOption;
-use Symfony\Component\Console\Output\ConsoleOutputInterface;
-use Symfony\Component\Console\Output\OutputInterface;
-
-/**
- * Dummy command which tells the user they are using an unsupported PHP.
- *
- * @copyright 2021 Chris Smith
- * @license MIT
- */
-final class AuditNotCompatibleCommand extends BaseCommand
-{
-    protected function configure()
-    {
-        // Configuration is copied from AuditCommand so that the command accepts the same inputs.
-        $this->setName('security-audit');
-        $this->setAliases(array('audit'));
-        $this->setDescription('Check packages for security advisories.');
-        $this->addOption(
-            'no-dev',
-            null,
-            InputOption::VALUE_NONE,
-            'Disable checking of development dependencies.'
-        );
-        $this->addOption(
-            'update',
-            null,
-            InputOption::VALUE_NONE,
-            'Update security advisory information if a new version is available.'
-        );
-    }
-
-    protected function execute(InputInterface $input, OutputInterface $output)
-    {
-        $output = $output instanceof ConsoleOutputInterface ? $output->getErrorOutput() : $output;
-
-        $output->writeln(sprintf('<error>Composer Audit is not compatible with PHP %s', PHP_VERSION));
-
-        return 2;
-    }
-}
diff --git a/src/Legacy/CommandProvider.php b/src/Legacy/CommandProvider.php
deleted file mode 100644
index 7b2e161..0000000
--- a/src/Legacy/CommandProvider.php
+++ /dev/null
@@ -1,18 +0,0 @@
-<?php
-
-namespace Cs278\ComposerAudit\Legacy;
-
-use Composer\Plugin\Capability\CommandProvider as CommandProviderCapability;
-
-/**
- * @internal This class is used when loading the plugin with PHP < 7.1.
- */
-final class CommandProvider implements CommandProviderCapability
-{
-    public function getCommands()
-    {
-        return array(
-            new AuditNotCompatibleCommand(),
-        );
-    }
-}
diff --git a/src/Legacy/ComposerPlugin.php b/src/Legacy/ComposerPlugin.php
deleted file mode 100644
index b4055d6..0000000
--- a/src/Legacy/ComposerPlugin.php
+++ /dev/null
@@ -1,44 +0,0 @@
-<?php
-
-namespace Cs278\ComposerAudit\Legacy;
-
-use Composer\Composer;
-use Composer\IO\IOInterface;
-use Composer\Plugin\Capable;
-use Composer\Plugin\PluginInterface;
-
-if (!class_exists(__NAMESPACE__.'\\ComposerPlugin', false)) {
-    if (\PHP_VERSION_ID >= 70100) {
-        \class_alias(substr(__NAMESPACE__, 0, strrpos(__NAMESPACE__, '\\')).'\\ComposerPlugin', __NAMESPACE__.'\\ComposerPlugin');
-    } else {
-        /**
-         * Composer Audit Plugin declaration.
-         *
-         * @internal This class is used when loading the plugin with PHP < 7.1.
-         */
-        final class ComposerPlugin implements PluginInterface, Capable
-        {
-            public function activate(Composer $composer, IOInterface $io)
-            {
-
-            }
-
-            public function deactivate(Composer $composer, IOInterface $io)
-            {
-
-            }
-
-            public function uninstall(Composer $composer, IOInterface $io)
-            {
-
-            }
-
-            public function getCapabilities()
-            {
-                return array(
-                    'Composer\\Plugin\\Capability\\CommandProvider' => __NAMESPACE__.'\\CommandProvider',
-                );
-            }
-        }
-    }
-}
diff --git a/src/Legacy/README b/src/Legacy/README
deleted file mode 100644
index 22f42be..0000000
--- a/src/Legacy/README
+++ /dev/null
@@ -1,2 +0,0 @@
-Code in this namespace must be compatible with the lowest PHP version that
-Composer supports.