Answer:
Your marketplace or community Terms and Conditions should set out the obligations of your users and activities that are prohibited. You should have the option to block users from your website when you would like to. Having obligations and prohibited activities in writing can make it much easier to explain or provide a warning to users of the website. As well making it easier to terminate the agreement if they breach these Terms and Conditions. You should ensure that if you have forums or comments on your website that users tick and agree to comply with these obligations when using your site.