I see following in HISTORY:
Disallow DROP TABLE/DROP INDEX inside a transaction block
However, it seems that this is not done with current?
test=# create table t1(i int);
CREATE
test=# begin;
BEGIN
test=# drop table t1;
NOTICE: Caution: DROP TABLE cannot be rolled back, so don't abort now
DROP
test=# end;
COMMIT
test=# \d
No relations found.
--
Tatsuo Ishii