HAMBURG, Germany, Nov. 16 — You wouldn't think of Gifty and Sylvia Oppong, 12 and 13 years old respectively, as much of a danger to Germany. They are, after all, only sisters going to school to learn German, and living with a mother whose proudest boast is that she's never taken a penny of public money.

And yet, the authorities in this affluent and historic river port city have issued formal orders for Gifty and Sylvia to be deported to their native Ghana. They did this even though that would separate the girls from their mother, a legal resident of Germany, and even though they have no family members ready to take care of them in Ghana. The deportations should take place, the authorities said, because the girls came to Germany even though their applications for visas had been denied, and the regulations must be respected.

"We have a law in Germany — and it is coercive and without any scope for discretion — saying that whoever enters Germany without the necessary visa has to go back where they came from," Dirk Nockemann, the Hamburg interior minister, said in an interview, defending the decision to expel the Oppong sisters.

"I think it is the sovereign right of every state to decide this way," he continued. "I am convinced that other states make the same decisions, especially the United States."

No doubt they do. Still, the case of Gifty and Sylvia Oppong has become a famous one in a Hamburg caught between a genuine, if perhaps exaggerated, fear of too many immigrants and a desire, in this case, that a sort of common sense prevail. The case also shows the influence of newly risen anti-immigration forces common elsewhere in Europe, as well as a counterreaction by people convinced by the Oppong sisters' case that the anti-immigration mood is going too far.

Hamburg has for many years been among Germany's most tolerant and liberal cities. It was governed for 44 years by the left-of-center Social Democrats, the party of Germany's current federal chancellor, Gerhard Schr?der. But the local political situation changed a couple of years ago with the arrival in power of a right-of-center coalition, whose main minority element was the brand-new Party for a Law and Order Offensive.

Thousands of Afghan refugees have been living here for years, alongside refugees from the former Yugoslavia and substantial numbers from West African countries like Ghana and Ivory Coast. There are, on the well-publicized negative side of this, gangs of Nigerian drug dealers and other criminals operating in Hamburg, which is also the place where Mohamed Atta and his friends lived and attended mosques before going to the United States to carry out the Sept. 11 terrorist attacks.

Gifty and Sylvia are neither drug dealers nor Muslim extremists. They are simply the daughters of a mother, Dorothy S?dorblom, a devout Seventh-day Adventist who left her home in Ghana 10 years ago for Germany, where she applied for political asylum. Given the right of temporary residence, Mrs. S?dorblom married a German man after a couple of years and got legal permanent residency status in this country.

Mrs. S?dorblom, who was a single mother, had been unable to bring her children with her when she first came to Germany. She left her two girls, then toddlers, in the care of her sister but, as she tells the story, her sister eventually stopped caring for them, telling Mrs. S?dorblom that she was "fed up." Mrs. S?dorblom, who works as a hotel chambermaid, tried repeatedly and with considerable fees paid to lawyers, to procure visas for her daughters — whom she had gotten into a boarding school in Ghana — so they could join her in Hamburg. But the German Embassy and then the German courts turned down a series of visa applications made over a period of five years.

Finally, last November, Mrs. S?dorblom said, Gifty and Sylvia were brought to Germany by an old Ghanaian friend who simply called their surprised mother and told her to pick them up. A few months later, the authorities learned of their presence and ordered them to leave.

The Party for a Law and Order Offensive has publicly pledged to see that the pace of deportations is roughly tripled, to 500 a month. With some 13,000 foreigners in Hamburg in "tolerated" status, meaning they are allowed to stay temporarily even though their papers are not in order, the pool of potential deportees is a large one. Gifty and Sylvia Oppong are in that pool, and though the public attention to their case seems to have led the city government not to enforce its earlier deportation order, nobody in their household knows what tomorrow will bring.

"Sometimes I cry and cry and cry," Mrs. S?dorblom said during an interview in her modest apartment, while Gifty and Sylvia sat on couches nearby. "I don't know what to do, so I just raise up my eyes to Jehovah."

Asked what she would like, Gifty, who says she wants to be a nurse, said: "We don't have any place to go. We just want to stay here with my mother."