Refuse een assignment because it 'cannot' be routed?

Dear colleagues,

in the discussion about assigning fixed address space to residential
always-on customers, I concluded that most ISPs are eager to provide their
customers with this service, even using it as a weapon in the competition
battle.
However in some countries apparently the contrary is going on. All ISPs
there offer 2 classes of DSL service: cheap subscriptions (low traffic,
dynamic ip, no options)  on one hand and an expensive 'pro' contract (high
traffic volume, static ip, router etc.) on the other.
Now a customer would like to get a static ip but does not want the router,
large volume etc so he does not want to pay 4 times as much per month
(real-life example) just to get a static ip.
If the customers sends a RIPE-141 request to the ISP, can the ISP assign a
range but not route it to the customer? Can it refuse the request on the
grounds that it cannot route the assigned range to a dynamic ip?
Or is the ISP obliged to assign a range and route it (no matter how,
presumably by assigning the customer a static ip anyway) ? With or without
additional (reasonable?) cost to the customer?

tia
best regards,
Herbert

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HB5351
Herbert Baerten
Network Manager HostIT Benelux