I am assuming you issue the rollback inside the trigger as that would affect all updates to that point.
I am also assuming that the error logging is occurring inside...

Going to say it again, it would help to see what the issue with the views are so that we can provide better answers.  We can't see what you see.

To be honest, with out seeing what you are working with it is hard to provide a good answer.

I came up with this:

CREATE TABLE SESSIONS(ID INT, SESSIONNAME VARCHAR(250), MAXSLOTS INT);

insert into SESSIONS
select 1, 'First Session', 5
union all
select 2, 'Second Session',3
union...