A guide to Twitter Violations and reporting Violations
Twitter is probably the best social media platform I have used to date. No rambling posts, a good community platform and messages are short and sweet allowing for better interactions between users. Unfortunately, like all social media there are those who use it to dole out vile abuse.
To combat this Twitter has some clear lines in terms of what they perceive as a violation of user rights.
The Twitter Rules

• Impersonation: You may not impersonate others through the Twitter service in a manner that does or is intended to mislead, confuse, or deceive others
• Trademark: We reserve the right to reclaim user names on behalf of businesses or individuals that hold legal claim or trademark on those user names. Accounts using business names and/or logos to mislead others will be permanently suspended.
• Privacy: You may not publish or post other people’s private and confidential information, such as credit card numbers, street address or Social Security/National Identity numbers, without their express authorization and permission.
• Violence and Threats: You may not publish or post direct, specific threats of violence against others.
• Copyright: We will respond to clear and complete notices of alleged copyright infringement. Our copyright procedures are set forth in the Terms of Service.
• Unlawful Use: You may not use our service for any unlawful purposes or in furtherance of illegal activities. International users agree to comply with all local laws regarding online conduct and acceptable content.
• Misuse of Twitter Badges: You may not use a Verified Account badge or Promoted Products badge unless it is provided by Twitter. Accounts using these badges as part of profile pictures, background images, or in a way that falsely implies affiliation with Twitter will be suspended.

 
Please note the highlighted paragraph on Unlawful Use :  We recommend that from the  March 3^rd  2012 if you live in Scotland and make a complaint regarding Sectarian or racist posts or posts containing threats that you explain to Twitter staff that these types of posts are illegal under the  ‘The Offensive Behaviour at Football and Threatening Communications (Scotland)’.This should ensure that all accounts breaking this law are closed down.
 

How To Report Violations

The Twitter Trust & Safety team responds to potential violations of the Twitter Rules and Terms of Service. Using the information below, find out what constitutes a violation, and what information you’ll need to provide to get the quickest resolution to a problem.
Here’s what we’ll require when you file a report:

• Your Twitter Username
• A detailed description of your issue
• Direct links to any Tweets you’d like us to review (to find the direct status links to individual Tweets, see our help page.)

Each policy page below has more information on the reporting topic and submitting a support ticket request.

Policy Issues

• Brand and Trademark Complaints
• Breach of Privacy
• Child Pornography
• Copyright Complaints
• Harassment and Violent Threats Policy
• Impersonation
• Name Squatting
• Reposting Others’ Content without Attribution
• Pornography: Twitter does remove obscene or pornographic images in either user profile pictures or user backgrounds. Report such images by filing a support ticket. We do not regulate content on external (non-Twitter) websites, nor do we regulate Tweets that link to content on external websites, including pornography.