Since 2012, the website Politwoops has tracked which tweets U.S. lawmakers delete from their Twitter accounts—usually due to innocent typos or simple errors, and sometimes due to more embarrassing mistakes. Last month, however, the site abruptly stopped working: The last deleted tweet listed on its main page, by Rep. Tammy Duckworth of Illinois, is dated May 15. Politwoops has not been updated in the two weeks since.

So what happened? Twitter did not respond to a request for comment, but a statement from Nicko Margolies of the Washington-based Sunlight Foundation, the open-government advocacy group that runs Politwoops, indicated the problem was on Twitter’s end:

Politwoops is dealing with an issue related to the access to Twitter data. We’ve appealed through Twitter’s support process and are waiting on a response. Unfortunately, in the meantime the site is not up-to-date.

In a blog post published at midnight on Friday, Margolies described Politwoops’ predicament as an “outage,” but the language of his statement to Gawker seems to suggest Twitter revoked Politwoops’ permission to use the Twitter API, or application program interface, through which software developers access Twitter’s database of tweets and users.

Twitter’s Developer Agreement & Policy, which governs usage of the site’s API, appears to forbid the deliberate preservation of any deleted tweets. Under the subheading “Maintain the Integrity of Twitter’s Products,” the document tells developers:

Only surface Twitter activity as it surfaced on Twitter. For example, your Service should execute the unfavorite and delete actions by removing all relevant Content, not by publicly displaying to other users that the Tweet is no longer favorited or has been deleted.

This would be a big impediment for Politwoops, whose entire purpose is publicly displaying tweets that have been deleted by public figures. In the past, the site apparently complied with Twitter’s demands by having each deleted tweet personally reviewed by a Sunlight Foundation staffer before publication (see sidebar). It’s unclear whether Twitter considered this loophole in compliance with their developer policy.

Margolies did not return subsequent requests for comment. And, as of today, Politwoops is still not working.

Update, 6/2/2015, 11 a.m.

A tipster writes in:

Hey—I’m close with Sunlight folks, and Twitter did block them. They knew they were breaking Twitter’s terms of service, and now Twitter is officially blocking them and not responding to email.

Update, 6/2/2015, 12:50 p.m.

Gabriela Schneider of the Sunlight Foundation writes in:

Hi Keenan,

Thanks for getting in touch. We’re working with Twitter and hope to have Politwoops back up soon.

Update, 6/3/2015, 6:30 p.m.

In a statement to Gawker, Twitter announced it will not restore Politwoops’ access to Twitter’s developer API.

If you know any more about this, please get in touch.