Displaying login window, or warning

Hello, one week ago i decided to lurk into meteor, and studied few tutorials, but i couldn’t find anywhere in the internet guide about creating something like login redirect - I want to have user see some annotation or warning if he click on “delete” button, when he doesn’t pass .allow test in my model.js with info that he should sign-in. How to achieve such task, so users could see that this functionality is available only for logged in user, or if they doesn’t have permissions to change something?

Best regards