THE European Community will hold an emergency meeting in The Hague today to settle on an EC response to Mikhail Gorbachev's ouster. NATO has also called an emergency meeting in Brussels today.The EC ministers are expected to come down hard - at least in rhetoric - on the Soviet power grab, which British Prime Minister John Major described as "unconstitutional." But the EC may be slow to act, reflecting differing views on strategy toward the Soviets among member states. Dutch Foreign Minister Hans van den Broeck, the EC president, said Monday the EC assumed the Soviets would "comply with their international obligations," such as the Soviet troop withdrawal from east Germany. A spokesman said no cut in $500 million in EC aid was planned. Mr. Van den Broeck said an "assessment of the situation" would also determine any action on economic ties with the Soviets. Senior British parliamentarians called for a rethinking of sweeping defense cuts saying Gorbachev's overthrow posed a serious problem for Britain and its policy. "There is an enormous military capability which is now in the hands of hard-liners," said Michael Mates, of the House of Commons Defense Committee. "It is something about which the West must be very cautious." Friends of Margaret Thatcher, the former prime minister, say she sees Gorbachev's downfall as a bitter personal blow. Mrs. Thatcher was the first world leader to recognize him as a man who could bring together East and West and who could end the decades of cruel Soviet oppression. French President Francois Mitterrand issued no response by Monday afternoon, but he faces opposition pressure to cut aid. For France, one of the key concerns determining its foreign policy since the fall of the Berlin Wall has been how to contain the ascending power of a reunited Germany. That preoccupation is likely to color how France responds to the Soviet crisis. France's skepticism toward Gorbachev kept the country from becoming a center of "Gorbymania" as other Western countries did, but at the same time a strong Soviet Union was seen as a valuable balance to Germany. Mr. Mitterrand has shown himself a fervent supporter of the status quo, be it in the Gulf, in Yugoslavia, or in Europe. The calls of Russian President Boris Yeltsin for the international community to "come to the aid" of his country's "legal power" may not receive from Paris the enthusiastic response sought.