Your article about US architects working in Britain ('Kohn Pedersen Fox rejects US registration criticisms', AJ 18.5.00) makes reference to the wider issue of practices being registered with the RIBA and thus gaining publicity by means of the Register of Practices and the Clients Advisory Service database.As you imply, when registering each year with the RIBA, practices sign a declaration stating that 80 per cent of the architects in the practice are RIBA corporate members.
Since being registered involves a fee, not adhering to the declaration in respect of the number of RIBA members is presumably a breach of contract between the RIBA and the practice concerned, calling into question the practice's relationship with the institute.
The RIBA does not need to take the matter on trust since it is straightforward to search the ARBWeb database, find out who is registered in any practice, and then check that against the RIBA web membership list. Kohn Pedersen Fox (KPF) has 12 registered architects at present on the register, including, as you say, LAPol isano and AEKohn; and anyone can check to see if indeed 10 of these are RIBA members.
KPF is the sort of reputable practice which one imagines would pay RIBA subscriptions for its staff and encourage RIBA membership as a matter of course, whether or not they felt that there was a marketing opportunity in so doing.
Tim Gough, Austin Winkley & Associates, London SE1