Russian President Vladimir Putin signed a law Friday completing the annexation of Crimea.
The ceremony at the Kremlin means Crimea has become part of the Russian Federation as two administrative districts, Crimea and the port city of Sevastopol.
Before signing the law, Putin hailed the incorporation of Crimea into Russian territory as a “remarkable event,” The Associated Press reported.
Western leaders and the new regime in Kiev have rejected the move, claiming Moscow’s actions constitute an illegal land grab.
Putin’s signature marked the end of an official process that he started on Tuesday with a passionate speech in front of members from both houses of parliament.
From there it was sent through the constitutional court and ratified unanimously by the lower and upper houses. However, after Putin gave his official support these stages were seen as a formality.
Earlier on Friday, Soviet chess legend-turned-political activist Garry Kasparov warned Western leaders in a Washington Post op-ed that "there is no dealing with" Putin and that only a show of strength could stop the Russian leader.
He also criticized Obama for taking the threat of troops off the table: "Nobody was asking for troops...but where Obama sees a gesture of peaceful intent, Putin sees more weakness."
The U.S. and E.U. slapped sanctions on dozens of Russian officials before and after Putin declared his intention to annex Crimea this week.
The Kremlin responded by imposing its own sanctions on top U.S. officials, including House Speaker John Boehner, Senate Majority Leader Harry Reid and Senator John McCain.
In an interview with CNBC on Friday, Swedish Prime Minister Fredrik Reinfeldt said the sanctions would impact Russia more than it was letting on, and that Moscow was only "hurting itself" with its course of action.
Reuters contributed to this report.