diff --git a/libimagentrytag/Cargo.toml b/libimagentrytag/Cargo.toml
index 69de9999..97cdde62 100644
--- a/libimagentrytag/Cargo.toml
+++ b/libimagentrytag/Cargo.toml
@@ -20,6 +20,7 @@ regex = "0.2"
 toml = "^0.4"
 itertools = "0.5"
 is-match = "0.1"
+filters = "0.1"
 
 [dependencies.libimagstore]
 path = "../libimagstore"
diff --git a/libimagentrytag/src/lib.rs b/libimagentrytag/src/lib.rs
index d933fb90..6cac9690 100644
--- a/libimagentrytag/src/lib.rs
+++ b/libimagentrytag/src/lib.rs
@@ -37,6 +37,7 @@ extern crate itertools;
 extern crate regex;
 extern crate toml;
 #[macro_use] extern crate is_match;
+extern crate filters;
 
 extern crate libimagstore;
 #[macro_use] extern crate libimagerror;
diff --git a/libimagentrytag/src/tag.rs b/libimagentrytag/src/tag.rs
index 28ecd934..cf3d6765 100644
--- a/libimagentrytag/src/tag.rs
+++ b/libimagentrytag/src/tag.rs
@@ -19,3 +19,19 @@
 
 pub type Tag = String;
 pub type TagSlice<'a> = &'a str;
+
+/// validator which can be used by clap to validate that a string is a valid tag
+pub fn is_tag(s: String) -> Result<(), String> {
+    use filters::filter::Filter;
+
+    let is_lower      = |s: &String| s.chars().all(|c| c.is_lowercase());
+    let no_whitespace = |s: &String| s.chars().all(|c| !c.is_whitespace());
+    let is_alphanum   = |s: &String| s.chars().all(|c| c.is_alphanumeric());
+
+    if is_lower.and(no_whitespace).and(is_alphanum).filter(&s) {
+        Ok(())
+    } else {
+        Err(format!("The string '{}' is not a valid tag", s))
+    }
+}
+