Tweets from prominent government officials that break the platform's rules but have been left online will be hidden behind a notice.
The company accepted it had not clearly communicated many of the decisions it had made in the past.
But the new notice will only be applied to tweets sent after 27 June.
Unclear
Twitter's critics say the platform does not enforce its rules evenly, allowing politicians to break its rules on abuse, harassment and incitement.
In the past, Twitter has defended some of its decisions by saying the tweets in question were "newsworthy".
For example, in September 2017 the company said it had decided to leave a controversial tweet by US President Donald Trump online.
In the tweet, Mr Trump said: "Just heard Foreign Minister of North Korea speak at UN. If he echoes thoughts of Little Rocket Man, they won't be around much longer!"
Many people interpreted the message as a threat to North Korea.
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Although Twitter decided the post was newsworthy, there was no indication of this on the Twitter app or website.
Rule breakers
Twitter did not say whether any particular politician had inspired the change to its rules.
Tweets placed behind the new notice will no longer appear in search results and will not be promoted by the platform's algorithms.