AT a press briefing on this week's round of negotiations among European Community foreign ministers preparing a profound revision of the EC's governing treaty, a spokesman for British Foreign Secretary Douglas Hurd announced that Britain would seek language to enforce animal rights."Don't laugh," the spokesman responded to a room full of snickering journalists more accustomed to following disputes over a European defense role and the fine points of European monetary union. "This is quite serious." Indeed, in the year-long talks pushing forward the Community's economic and political integration, which will culminate in the Netherlands town of Maastricht next Tuesday, nothing escapes close scrutiny. That is why Spain responded so swiftly to Britain's proposal to bring animal rights within Community jurisdiction. "We are not opposed to a narrowly defined declaration on animal rights," said one Spanish official in Brussels, "but we don't want to see it affecting popular traditions and national festivals." In other words, Spain doesn't want the Community touching its bullfights. The British have their own reasons for making the animal rights proposal. The issue is extremely sensitive in Britain. And "it's an important element" in bringing often reluctant citizens into what, for most of them, remains a distant, bureaucratic process, the British spokesman said. In its present form the declaration "would not be binding," the spokesman said, and would apply to EC agriculture regulations, animal transport, and research. But "it could be," he added, that an adopted text would develop into something more constraining in the future. And that is what worries Spain. "This could not be considered as opening the door to a wider definition farther down the road," the Spanish official says. "It is not within Community jurisdiction." As the generally pro-Community and federalist Spanish know, such doors, once opened, are nearly impossible to shut. The British, with their common-law tradition and years of Community experience, are keenly aware of how the process works. Some European analysts say former British Prime Minister Margaret Thatcher unwittingly helped push the Community in the federal direction she so abhors when she signed on to the EC's Single Market Act in 1986. She saw it as the fulfillment of an ultimate free trade zone where people, goods, services, and capital would circulate freely. That it will be. But by raising fundamental questions about how such an integrated and borderless Community should function, that act has been a central trigger in the drive for deeper political integration. Areas such as immigration, justice, and social welfare, which Britain would leave to the member states, are gradually and naturally drawn under Community oversight. With each word holding full meaning for the future, no one lets anything pass by as mere semantics. One of Tuesday's major arguments sure to provide fireworks in Maastricht was over the use of the word "federal" to describe the Community's goal in the treaty's preamble and elsewhere. The British say they will not sign anything including the word. French Foreign Minister Roland Dumas said the word would come out, replaced by a longer formula meaning the same thing. "We'll have the content without [the word] that contains it." The British also fought for - and won - language allowing a member state to place the face of its own sovereign on an eventual single European currency. It was further indication of the care being taken now with wording likely to have an important impact in the future. Spanish bullfights may still be around by the end of the century, but British tourists will probably pay to see them with a European bank note carrying the face of their own monarch.