CMS Cameron McKenna and its German member firm CMS Hasche Sigle Eschenlohr Peltzer Schäfer are acting on the sale of Germany's largest internet company.
UK firm Energis is buying Distefora Holding's 75 per cent stake in Ision Internet, a Neuer Markt listed company, for just under £500m.
The deal, which is due to be completed at the end of January following approval by the German competition authorities, consists of a mixture of cash and Energis shares.
However, the deal was particularly unusual as it involved a unique combination of German and UK law.
Camerons corporate technology partner David Bresnick says that although German law essentially governed the deal, it was based on the UK legal system because Energis is a UK company. He says: "We have not got large stacks of 'off the shelf' precedents for that."
Christian von Lenthe led the team for Hasche Sigle. The Camerons team was led by corporate partner Martin Mendelssohn and Bresnick.
Clifford Chance acted for long-term client Energis in both the UK and Germany, with UK corporate partner Mark Poulton leading the deal.
Distefora is a long-term client of Hasche Sigle. Camerons has also worked for the client before, although it is usually instructed by Ision, one of Europe's largest internet companies.
Bresnick says that he expects Ision, which manages websites, to be advised by Energis' external firms in the future. But he adds that Distefora has sold the company in a bid to strengthen its core media activities, and expects this refocus to continue to be a source of work in the future.
Both Camerons and Hasche Sigle were asked to work on the deal at the beginning of December. Despite working together on the deal, the two firms will bill the client separately.
Hasche Sigle is one of five alliance firms working under the CMS banner in Europe.