We strongly recommend you to bring your passport or form of ID valid for entering Denmark, even though you are traveling from a country member of Schengen. People going to the G8-summit in Rostock in 2008 were checked at the Danish/German border and people not possessing a passport or other valid ID were immediately sent back. We expect the same to happen during the COP15.
Border support teams are being set up at the German/Danish border and the Swedish/Danish border, together with lawyer support from Copenhagen. There will be organized pick up spots for people being denied entrance. More specific info can be found here.
If you need help or want to help out with border issues, please contact borderInfo.dec09@gmail.com
For up-to-date border crossing information, you can check out (starting from December 7) this website: http://borderwatchcop15.blogsport.de
The phone number to contact for help in Flensburg (German/Danish border) is 004915153610132.
Contact in Rostock:
grenzsolicop15-rostock@riseup.net
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Phone 0049 (0)15224551075
Contact in Malmoe (Swedish/Danish border): 0046 760188650
For information on the SMS system for border support for people flying to Copenhagen, please check this PDF.
Source: http://www.climate-justice-action.org/practical-info/copenhagen-info/#Border%20control