The court session was delayed by an hour after some 4,000 to 10,000 supporters of both camps gathered in front of the building early Wednesday, preventing the judges from entering the court for a second day of hearings on the decree.
Sixteen of 18 judges are present at the court session, with 12 votes required for a quorum. The court consists of six judges appointed on the presidential quota, six on the parliamentary quota and six from the judges' convention. Judges said Tuesday it would take about ten days to decide on the matter. Both sides in the conflict, President Viktor Yushchenko and his arch rival Prime Minister Viktor Yanukovych, have said they are ready to abide by any court decision and ruled out the use of force.
The president signed the decree April 2 after 11 opposition members defected to the ruling coalition backing the prime minister. The coalition refused to obey the order and referred it to the Constitutional Court.
Anatoliy Lutsenko of the pro-presidential opposition party Our Ukraine said police had beaten up opposition members near the building Wednesday morning.
"When the judges were led through the gates to the Constitutional Court, a special police squad beat up opposition members," Lutsenko said, adding that some of them had been injured.
David Zhvaniya, another opposition deputy, said that the ruling coalition stood behind the police actions.
Prime Minister Viktor Yanukovych has the support of the Interior Ministry, while President Viktor Yushchenko has the military behind him.
In view of the events, Yanukovych called an emergency government session, and said a compromise could still be reached with the president and the opposition before the Constitutional Court makes its decision.
"There are still opportunities for resuming the dialogue and reaching a compromise," Yanukovych said, opening of the session.
Yushchenko has repeatedly said he would not backtrack on his decree, but admitted there was a possibility of delaying the early elections scheduled for May 27.
Another opposition leader, former premier Yulia Tymoshenko and Yushchenko's ally in the 2004 "orange revolution," has been pursuing a radical position in the crisis. She said Tuesday night that the Constitutional Court was corrupt and its session was "a farce".
"The Constitutional Court in its present form cannot and must not be an arbiter," she said, urging the president to recall judges appointed on his quota.
A former associate of Tymoshenko, who quit the Yulia Tymoshenko Bloc in late 2006, said the "orange princess" had asked him for money to bribe the Constitutional Court judges.
"Yulia ... promised to buy me a bottle of cognac if she fails to bribe the judges, and asked me to give her money for the purpose," Mikhail Brodsky said.
