To have users banned in ns2 is a bit harder than in cs:s due to the lack of server side demo recording (or any demo recording) to produce automated evidence. Currently all server logs are avaliable here for evidence: ftp://ns2.ibisgaming.com/
In some cases you may need to record a video using fraps in order to get a ban that will stick if contested. I urge you to please post in the unknown worlds forums requesting that server side demo recording like hltv be added to NS2 to greatly simplify the process of catching hackers in NS2.
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Remember to make ban requests in the normal locations in the forums but with the logs or other evidence instead of demos.