diff --git a/tools/aconfig/src/commands.rs b/tools/aconfig/src/commands.rs
index bd09e24..ab5b0f2 100644
--- a/tools/aconfig/src/commands.rs
+++ b/tools/aconfig/src/commands.rs
@@ -52,10 +52,15 @@
     pub contents: Vec<u8>,
 }
 
-const DEFAULT_FLAG_STATE: ProtoFlagState = ProtoFlagState::DISABLED;
-const DEFAULT_FLAG_PERMISSION: ProtoFlagPermission = ProtoFlagPermission::READ_WRITE;
+pub const DEFAULT_FLAG_STATE: ProtoFlagState = ProtoFlagState::DISABLED;
+pub const DEFAULT_FLAG_PERMISSION: ProtoFlagPermission = ProtoFlagPermission::READ_WRITE;
 
-pub fn parse_flags(package: &str, declarations: Vec<Input>, values: Vec<Input>) -> Result<Vec<u8>> {
+pub fn parse_flags(
+    package: &str,
+    declarations: Vec<Input>,
+    values: Vec<Input>,
+    default_permission: ProtoFlagPermission,
+) -> Result<Vec<u8>> {
     let mut parsed_flags = ProtoParsedFlags::new();
 
     for mut input in declarations {
@@ -86,11 +91,11 @@
             parsed_flag.set_description(flag_declaration.take_description());
             parsed_flag.bug.append(&mut flag_declaration.bug);
             parsed_flag.set_state(DEFAULT_FLAG_STATE);
-            parsed_flag.set_permission(DEFAULT_FLAG_PERMISSION);
+            parsed_flag.set_permission(default_permission);
             let mut tracepoint = ProtoTracepoint::new();
             tracepoint.set_source(input.source.clone());
             tracepoint.set_state(DEFAULT_FLAG_STATE);
-            tracepoint.set_permission(DEFAULT_FLAG_PERMISSION);
+            tracepoint.set_permission(default_permission);
             parsed_flag.trace.push(tracepoint);
 
             // verify ParsedFlag looks reasonable
@@ -328,6 +333,36 @@
     }
 
     #[test]
+    fn test_parse_flags_setting_default() {
+        let first_flag = r#"
+        package: "com.first"
+        flag {
+            name: "first"
+            namespace: "first_ns"
+            description: "This is the description of the first flag."
+            bug: "123"
+        }
+        "#;
+        let declaration =
+            vec![Input { source: "momery".to_string(), reader: Box::new(first_flag.as_bytes()) }];
+        let value: Vec<Input> = vec![];
+
+        let flags_bytes = crate::commands::parse_flags(
+            "com.first",
+            declaration,
+            value,
+            ProtoFlagPermission::READ_ONLY,
+        )
+        .unwrap();
+        let parsed_flags =
+            crate::protos::parsed_flags::try_from_binary_proto(&flags_bytes).unwrap();
+        assert_eq!(1, parsed_flags.parsed_flag.len());
+        let parsed_flag = parsed_flags.parsed_flag.first().unwrap();
+        assert_eq!(ProtoFlagState::DISABLED, parsed_flag.state());
+        assert_eq!(ProtoFlagPermission::READ_ONLY, parsed_flag.permission());
+    }
+
+    #[test]
     fn test_create_device_config_defaults() {
         let input = parse_test_flags_as_input();
         let bytes = create_device_config_defaults(input).unwrap();
diff --git a/tools/aconfig/src/main.rs b/tools/aconfig/src/main.rs
index 920b761..84073f7 100644
--- a/tools/aconfig/src/main.rs
+++ b/tools/aconfig/src/main.rs
@@ -44,6 +44,14 @@
                 .arg(Arg::new("package").long("package").required(true))
                 .arg(Arg::new("declarations").long("declarations").action(ArgAction::Append))
                 .arg(Arg::new("values").long("values").action(ArgAction::Append))
+                .arg(
+                    Arg::new("default-permission")
+                        .long("default-permission")
+                        .value_parser(protos::flag_permission::parse_from_str)
+                        .default_value(protos::flag_permission::to_string(
+                            &commands::DEFAULT_FLAG_PERMISSION,
+                        )),
+                )
                 .arg(Arg::new("cache").long("cache").required(true)),
         )
         .subcommand(
@@ -161,7 +169,9 @@
             let package = get_required_arg::<String>(sub_matches, "package")?;
             let declarations = open_zero_or_more_files(sub_matches, "declarations")?;
             let values = open_zero_or_more_files(sub_matches, "values")?;
-            let output = commands::parse_flags(package, declarations, values)
+            let default_permission =
+                get_required_arg::<protos::ProtoFlagPermission>(sub_matches, "default-permission")?;
+            let output = commands::parse_flags(package, declarations, values, *default_permission)
                 .context("failed to create cache")?;
             let path = get_required_arg::<String>(sub_matches, "cache")?;
             write_output_to_file_or_stdout(path, &output)?;
diff --git a/tools/aconfig/src/protos.rs b/tools/aconfig/src/protos.rs
index 2ab6e05..c3911e5 100644
--- a/tools/aconfig/src/protos.rs
+++ b/tools/aconfig/src/protos.rs
@@ -156,6 +156,26 @@
     }
 }
 
+pub mod flag_permission {
+    use super::*;
+    use anyhow::bail;
+
+    pub fn parse_from_str(permission: &str) -> Result<ProtoFlagPermission> {
+        match permission.to_ascii_lowercase().as_str() {
+            "read_write" => Ok(ProtoFlagPermission::READ_WRITE),
+            "read_only" => Ok(ProtoFlagPermission::READ_ONLY),
+            _ => bail!("Permission needs to be read_only or read_write."),
+        }
+    }
+
+    pub fn to_string(permission: &ProtoFlagPermission) -> &str {
+        match permission {
+            ProtoFlagPermission::READ_WRITE => "read_write",
+            ProtoFlagPermission::READ_ONLY => "read_only",
+        }
+    }
+}
+
 pub mod tracepoint {
     use super::*;
     use anyhow::ensure;
diff --git a/tools/aconfig/src/test.rs b/tools/aconfig/src/test.rs
index 14beb93..6c27885 100644
--- a/tools/aconfig/src/test.rs
+++ b/tools/aconfig/src/test.rs
@@ -118,6 +118,7 @@
                     reader: Box::new(include_bytes!("../tests/second.values").as_slice()),
                 },
             ],
+            crate::commands::DEFAULT_FLAG_PERMISSION,
         )
         .unwrap();
         crate::protos::parsed_flags::try_from_binary_proto(&bytes).unwrap()