[mjevans]

RIPE approved prefix lengths for end customers are /48, /52, /56, /60, and /64; though the prefixes longer than /56 are strongly discouraged and probably reflect either an ISP that doesn't get IPv6 or that is anti-consumer if they do.

https://www.ripe.net/publications/docs/ripe-690#4-2--prefix-...

... "Each hexadecimal character in an IPv6 prefix represents one nibble, which is 4 bits. The length of a delegated prefix should therefore always be a multiple of 4.

A single network at a customer site will be a /64. At present, RIR policies permit assignment of a /48 per site, so the possible options when choosing a prefix size to delegate are /48, /52, /56, /60 and /64.

...

The following sections explain why /48 and /56 are the recommended prefix assignment sizes for end customers.

...

It is strongly discouraged to assign prefixes longer than /56 unless there are very strong and unsolvable technical reasons for doing this."

[tsimionescu]

Is RIPE a law? Can they force my ISP to give me a /56 if they're giving me a /128?

[zamadatix]

It's not law but going to hurt your ISP to not give at minimum a /64 way more than it's going to hurt anyone else as everything is made to make doing so easy from standards all the way down to hardware. Besides RIPE is going to hand them a /32 which is ~4 billion /64s without question and will keep doing that 'til the cows come home so it's not like trying to keep all of the customers in a single /64 saves them from running out of anything. Shoot I even got a /32 for a single non-ISP company without much hassle.

Also RIPE reserves the ability to retract the ISP's IPv6 space, though I really doubt it'd come to that. A lot of the original large swaths of IPv4 were considered owned not leased, that is no longer.