diff --git a/src/commands/CommandHandler.ts b/src/commands/CommandHandler.ts
index ea12167..4d96780 100644
--- a/src/commands/CommandHandler.ts
+++ b/src/commands/CommandHandler.ts
@@ -17,7 +17,7 @@ limitations under the License.
 import { Mjolnir } from "../Mjolnir";
 import { execStatusCommand } from "./StatusCommand";
 import { execBanCommand, execUnbanCommand } from "./UnbanBanCommand";
-import { execDumpRulesCommand } from "./DumpRulesCommand";
+import { execDumpRulesCommand, execRulesMatchingCommand } from "./DumpRulesCommand";
 import { extractRequestError, LogService, RichReply } from "matrix-bot-sdk";
 import { htmlEscape } from "../utils";
 import { execSyncCommand } from "./SyncCommand";
@@ -59,6 +59,8 @@ export async function handleCommand(roomId: string, event: { content: { body: st
             return await execBanCommand(roomId, event, mjolnir, parts);
         } else if (parts[1] === 'unban' && parts.length > 2) {
             return await execUnbanCommand(roomId, event, mjolnir, parts);
+        } else if (parts[1] === 'rules' && parts.length === 4 && parts[2] === 'matching') {
+            return await execRulesMatchingCommand(roomId, event, mjolnir, parts[3])
         } else if (parts[1] === 'rules') {
             return await execDumpRulesCommand(roomId, event, mjolnir);
         } else if (parts[1] === 'sync') {
@@ -133,6 +135,7 @@ export async function handleCommand(roomId: string, event: { content: { body: st
                 "!mjolnir redact <event permalink>                                   - Redacts a message by permalink\n" +
                 "!mjolnir kick <glob> [room alias/ID] [reason]                    - Kicks a user or all of those matching a glob in a particular room or all protected rooms\n" +
                 "!mjolnir rules                                                      - Lists the rules currently in use by Mjolnir\n" +
+                "!mjolnir rules matching <user|room|server>                          - Lists the rules in use that will match this entity e.g. `!rules matching @foo:example.com` will show all the user and server rules, including globs, that match this user." +
                 "!mjolnir sync                                                       - Force updates of all lists and re-apply rules\n" +
                 "!mjolnir verify                                                     - Ensures Mjolnir can moderate all your rooms\n" +
                 "!mjolnir list create <shortcode> <alias localpart>                  - Creates a new ban list with the given shortcode and alias\n" +
diff --git a/src/commands/DumpRulesCommand.ts b/src/commands/DumpRulesCommand.ts
index a2ee142..2c6c3d7 100644
--- a/src/commands/DumpRulesCommand.ts
+++ b/src/commands/DumpRulesCommand.ts
@@ -14,10 +14,63 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import { Mjolnir } from "../Mjolnir";
 import { RichReply } from "matrix-bot-sdk";
+import { Mjolnir } from "../Mjolnir";
+import { RULE_ROOM, RULE_SERVER, RULE_USER } from "../models/BanList";
 import { htmlEscape } from "../utils";
 
+/**
+ * List all of the rules that match a given entity.
+ * The reason why you want to test against all rules and not just e.g. user or server is because
+ * there are situations where rules of different types can ban other entities e.g. server ACL can cause users to be banned.
+ * @param roomId The room the command is from.
+ * @param event The event containing the command.
+ * @param mjolnir A mjolnir to fetch the watched lists from.
+ * @param entity a user, room id or server.
+ * @returns When a response has been sent to the command.
+ */
+export async function execRulesMatchingCommand(roomId: string, event: any, mjolnir: Mjolnir, entity: string) {
+    let html = "";
+    let text = "";
+    for (const list of mjolnir.lists) {
+        const matches =  list.rulesMatchingEntity(entity)
+
+        if (matches.length === 0) {
+            continue;
+        }
+
+        const matchesInfo = `Found ${matches.length} ` + (matches.length === 1 ? 'match:' : 'matches:');
+        const shortcodeInfo = list.listShortcode ? ` (shortcode: ${htmlEscape(list.listShortcode)})` : '';
+
+        html += `<a href="${htmlEscape(list.roomRef)}">${htmlEscape(list.roomId)}</a>${shortcodeInfo} ${matchesInfo}<br/><ul>`;
+        text += `${list.roomRef}${shortcodeInfo} ${matchesInfo}:\n`;
+
+        for (const rule of matches) {
+            // If we know the rule kind, we will give it a readable name, otherwise just use its name.
+            let ruleKind: string = rule.kind;
+            if (ruleKind === RULE_USER) {
+                ruleKind = 'user';
+            } else if (ruleKind === RULE_SERVER) {
+                ruleKind = 'server';
+            } else if (ruleKind === RULE_ROOM) {
+                ruleKind = 'room';
+            }
+            html += `<li>${htmlEscape(ruleKind)} (<code>${htmlEscape(rule.recommendation ?? "")}</code>): <code>${htmlEscape(rule.entity)}</code> (${htmlEscape(rule.reason)})</li>`;
+            text += `* ${ruleKind} (${rule.recommendation}): ${rule.entity} (${rule.reason})\n`;
+        }
+
+        html += "</ul>";
+    }
+
+    if (text.length === 0) {
+        html += `No results for ${htmlEscape(entity)}`;
+        text += `No results for ${entity}`;
+    }
+    const reply = RichReply.createFor(roomId, event, text, html);
+    reply["msgtype"] = "m.notice";
+    return mjolnir.client.sendMessage(roomId, reply);
+}
+
 // !mjolnir rules
 export async function execDumpRulesCommand(roomId: string, event: any, mjolnir: Mjolnir) {
     let html = "<b>Rules currently in use:</b><br/>";
diff --git a/src/models/BanList.ts b/src/models/BanList.ts
index 3b0d0a4..3b56f7f 100644
--- a/src/models/BanList.ts
+++ b/src/models/BanList.ts
@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import { extractRequestError, LogService, MatrixClient } from "matrix-bot-sdk";
+import { extractRequestError, LogService, MatrixClient, UserID } from "matrix-bot-sdk";
 import { EventEmitter } from "events";
 import { ListRule, RECOMMENDATION_BAN } from "./ListRule";
 
@@ -182,6 +182,38 @@ class BanList extends EventEmitter {
         return [...this.serverRules, ...this.userRules, ...this.roomRules];
     }
 
+    /**
+     * Return all of the rules in this list that will match the provided entity.
+     * If the entity is a user, then we match the domain part against server rules too.
+     * @param ruleKind The type of rule for the entity e.g. `RULE_USER`.
+     * @param entity The entity to test e.g. the user id, server name or a room id.
+     * @returns All of the rules that match this entity.
+     */
+    public rulesMatchingEntity(entity: string, ruleKind?: string): ListRule[] {
+        const ruleTypeOf: (entityPart: string) => string = (entityPart: string) => {
+            if (ruleKind) {
+                return ruleKind;
+            } else if (entityPart.startsWith("#") || entityPart.startsWith("#")) {
+                return RULE_ROOM;
+            } else if (entity.startsWith("@")) {
+                return RULE_USER;
+            } else {
+                return RULE_SERVER;
+            }
+        };
+
+        if (ruleTypeOf(entity) === RULE_USER) {
+            // We special case because want to see whether a server ban is preventing this user from participating too.
+            const userId = new UserID(entity);
+            return [
+                ...this.userRules.filter(rule => rule.isMatch(entity)),
+                ...this.serverRules.filter(rule => rule.isMatch(userId.domain))
+            ]
+        } else {
+            return this.rulesOfKind(ruleTypeOf(entity)).filter(rule => rule.isMatch(entity));
+        }
+    }
+
     /**
      * Remove all rules in the banList for this entity that have the same state key (as when we ban them)
      * by searching for rules that have legacy state types.